Sea to Summit - Thermolite Reactor Sleeping Bag Liner

I went hiking/camping last weekend and almost did not bring this along due to a warmer than average weather forecast. Ultimately, I decided it was so light it was worth the extra few ounces. Around 3 a.m. the wind on the mountain really picked up and it was cutting right through my sleeping bag. I pulled this liner out and and almost immediately felt the difference. This made the difference between a miserable night and being too cozy in the morning to want to get up.

I've used this liner twice so far. Once with a 25 degree bag in New Hampshire with temps in the teens and again in Vermont with my 0 degree bag when temps were single digits. It didn't turn my bags into sauna's but I definitely noticed a difference to the overall temp comfort of them. What I actually liked the most about it was how it seperated me from the icky clammy feeling that bags get due to moisture; like in winter when my head is tucked inside the bag and I'm breathing inside it! I was very surpised at how strong the liner material is. It looks very flimzy and tearable but is actually quite strong. I'm looking forward to trying it this summer with a thin sheet instead of carrying a sleeping bag.

Bought this to extend my 20° rated bag. It worked amazingly well. I was toasty warm in 10° weather.

I can't tell you how this will hold up, I got it yesterday. However, last night I slept outside in just it, no tent no sleeping bag, on a 50(ish) degree night and was as comfortable as I have ever been. I got this because the synthetic sleeping bag I've had for nearly 14 years is no longer even close to adequate, but I can't afford any of the fancy bags I would like. It is sufficient that in warmer conditions it will be the only bag I take and in colder conditions I will be relieved to have the added layer for so little space. I will get back to you on the durability. I am a rough sleeper so being a little resistant to a nightly thrashing is a must for me. ;)

I used this during 4 days of camping last week at Yosemite. My down sleeping bag is rated for something like 30'F, which as you know, isn't necessarily warm enough for temps in the 30s. I was surprised by how much of a difference this liner makes. I had forgotten to use it at first and even with cozy PJs and my down jacket on, I was too cold to go to sleep. When I added the liner, the difference was immediate.

So I used this every night in Iraq for a year, whether sleeping on base or in the sand, and it never ripped. Since I got back (2 years ago!) I've been using the same liner, still no rips, tears, or anything like that, and that's with one full year's worth of wear and tear and washings plus 2 more years of part-time use.

I bought this liner for a trip to a White Mountain hut. It was expected to be -10 degrees or lower and I only have a bag rated to 18 degrees. The liner worked like a charm. It was exactly 0 in the hut, but the liner kept me warm all night. Brilliant.

This liner is very good. I have used it a few times in conjunction with a zero degree no-name bag that was stuffed for many months... Lets call it a 10-15 degree. Anyway, it helped it out wonderfully, keeping me very warm, and it fit well in the bag, too.

i have used this liner 5 nights now, in preparation for a longer trip coming up...

I bought this for a 7 day Kilimanjaro trek & was SO happy to have it when the zipper on my rental sleeping bag broke. It was super warm and comfortable and I found it very easy to get in & out of in my small tent. Probably my favorite comfort item the whole trip!

Adds warmth, comfort, and protection to your sleeping bag, packs down to nothing, and is easy to clean. I've used this all season - either insider the bag or by itself when the nights are warm. Fantastic piece of kit!

When I was purchasing my new sleeping bag the sales associate recommended this to add warmth and to help extend the life of my bag. At first I thought they were just trying to sell me add ons that I really didn't need and I was hesitant at first but after carrying it around the store for a while I figured I could try it out and always return it. The material of the liner is super thin so I was skeptical on its ability make my bag warmer. I'm SO glad I purchased it! I was grateful to have this liner with me on cold nights. I can really tell the difference and agree it probably adds 10 degrees of warmth which is great for a cold sleeper like me! I have even used the liner as a super light sleeping bag on warm summer nights. It packs a lot of warmth in that small package!

Took camping in Cascades in early June. Temps in the low 30s. Slept on the REI Camp bed 3.5 inside a Northface Phantom 32 dressed in turtleneck and REI thermal tops and bottoms and light mittens and REI beanie PLUS this sleep sack and was fine. I'm not sure how much the sleep sack added but I slept fine. It was only a slight challenge getting into it but once inside no problem. I plan to carry this sleep sack when visiting friends so I don't have to dirty their sheets and when traveling to lessen possible contact with bedbugs. The sack feels good and packs very small.

Purchased this liner to add a bit warmth to a new down bag, plus wanted to keep the bag clean. It's been a great addition to our Summer and Fall backcountry trips above 8,000' where it the temp drops off quite a bit at night. Thus far it has been versitile enough to add the extra warmth, but the stated amount of 15deg is a bit optimistic, but on warmer evenings (40-50deg) I found myself using just this liner and being very comfortable. The greatest bonus of this liner is that it is soft and very light for the amount of heat retention it has. It cleans up easy and doesn't retain much if any moisture. I've been impressed with this liner and just picked one up for my wife at the [...]. We also fly a lot and I see us taking this with us on the plane too.

Great product. I used it in New Hampshire a few weekends ago (1/17/09) where it got to negative temps. I have the REI Kilo Flash 40 degree bag and had the thermolite liner. I was on a thermarest prolite 3 short sleeping pad with an emergency blanket below that. I was also bundled up in clothes and even though the temp got to -10, I was warm all night. This is a great piece and I was surprised at how much warmth it added. It is very lightweight and very small. If you are a backpacker like me, you need to get this.

I run cold and use a 25* down sleeping bag. Recently went camping when temps dropped down to the 30s over night. I definitely appreciated having this liner. I was able to cinch the drawstring above my shoulders to trap the heat in and slept very comfortably. The liner is easy to wash and will prevent my sleeping bag from accumulating too much grime.

Use this in my 20 degrees bag when it gets below freezing. I'm a cold sleeper & this does add warmth. Also nice to keep my bag clean(er).

This liner is pretty handy. I got it mainly because I didn't want to drop $300+ on a sleeping bag for winters in the rocky mountains. It adds significant warmth to my bag with very little weight. I also use it as a stand alone when I am in warmer climates (like Hawai'i) for backpacking. With a tarp, a hammock and this liner, you can travel pretty light. Its also nice for hanging out in the hammock when its not all that warm out. The black color helps even more to keep you toasty.

I brought it before my solo trip to Morocco in Dec. I stayed in the desert for 3 nights, which were freezing cold. I found myself non-stop shaking for 4 hours with 2 blankets on during the middle of night. I remembered that I had the linear in my backpack, pulled it out, wrapped it around me, and I felt much warmer after a short period of time. Then I went climbing Mt. Toubkal, and this linear (along with my down sleeping bag) kept me toasted. I even started to sweat a bit. Awesome!

I recently took this liner to the top of North Dome in Yosemite with a 40 degree quilt and a 3.2 r-value sleeping pad. The overnight temps were in the low 40s and I was incredibly warm. I also love that this liner stretches to move with you. The silk ones don't stretch which can be restrictive. Highly recommend.

I find that sleeping bag liners, for the most part, don't work well for me. Using one would be effective in keeping a bag clean, but I'm confronted with the problem of getting tangled up and the awkwardness of getting in and out of my sleeping bag. However a liner, like the Sea to Summit Thermolite, can be a good addition to adding more warmth when needed without paying the price of a warmer sleeping bag. I think the increased warmth of 14 degrees on the light weight liner that I purchased maybe optimistic, but I felt it performed well enough in turning my 41-degree rated sleeping bag to closer to a 31-degree bag during an early October overnight wilderness trip where the night temperature pushed the limits of my sleeping bag. Liners are intended to be used on the inside of a bag. All though, for those who are bothered by the problem of getting tangled up and need the gain of a little additional warmth, try slipping it over the outside of your sleeping bag like a bivy sack.

This is a great addition to your sleeping bag setup and makes it warmer. It also works like a bedsheet and keeps your sleeping bag cleaner. It's easier to wash this liner when it gets dirty instead of your bag. It's also very comfortable against your skin.

It works, I paired this with my 45 deg down bag and it I was fine down to 32 deg.

Outstanding liner. I got caught on an 8 day trip in the mountains with a wet down bag on day 2. Fortunately I had this liner which kept me warm and safe despite the constant snow until I was out of there.

So there isn't a "long" version available on the site (as of now) and the dimensions don't correlate to height very well. I'm 6'2" and it says 82"x35", but most of the 85" is used up by the portion under your head...so it does not reach my shoulders unless I push/stretch myself into the footbox which isn't very relaxing haha. It seems nice and warm, also very stretchy which is good because you have to wiggle into it. I would have kept it if it was longer! Decent price and seems cozy and well made.

Brought this along for an overnight in the Shenandoah in late October along with an older 30 degree primaloft bag that had been stored in a small bag. Woke up cold in about 35 degree weather at 3AM, wiggled into this and cinched everything down and slept just fine after that in long underwear and a hat. Would have been a very long and cold night without it. Takes up almost no room and was the difference between shivering all night and sleeping. I’m 6’2” and 215 lbs, and this fit just fine.

Pack this for backpacking trips when the weather is iffy, and it comes through. Gets you the extra warmth you need to stay comfortable when the temperature dips.

Really nice lightweight liner. Packs very small and adds considerable warmth for its weight. I pair this up with a lafuma 40 degree down bag and I use this combo for everything except snow camping. It did obsorb a little bit of camping smell, (campfire) but that just means its keeping the smell and smoke out of my sleeping bag. I would highly recommend this liner to anyone that uses an ultralight summer bag.

This is easily the best item I've purchased for backpacking.

I bought a liner primarily to help me supplement my usual down quilt on a trip that would involve some high-elevation nights in November, and to protect said quilt from all the hiking grime on my body and clothing. I've been pretty happy with it and use it all the time now.

The cocoon sack is warm and a nice fabric to lay against. I bought this for a couple backpacking trip to use in my sleeping bag as a barrier between the bag and for extra warmth. It did all of the above, and is easy to wash.

Purchased for a winter trip to add a few degrees to my bag. Did the trick and added a little extra comfort on a couple of cold nights.

I'm not sure why some people feel that this liner is not warm. I purchased one for both my wife and myself and so far we love them.

The biggest pro to this is it's entire lack of cons. It's lightweight, takes very little space, or essentially none if rolled up in your sleeping bag. Sure, it's thin and you might think it would rip to shreds, but do your t-shirts rip when all you do is sleep in them?

I haven't tried this as an actual sleeping bag liner. I've only used this on a summer hiking trip when it was quite hot out. It worked great in my hammock so I wouldn't have to pack my full bag that would have been too warm anyway. Very soft and comfortable and great quality!

The perfect solution for those of us who like to sleep under our mummy bags, rather than in them. Does away with sweaty nights on a sleeping pad and provides enough warmth on its own for nights in the 60's. Just back from a few wet days/nights at Cape Alava, temps in the high 40's and low 50's at night. This liner was the perfect compliment to my lightweight 40 degree down bag. Worth the weight.

Definitely helped keep me warm. It took a few nights to figure out how to tighten the drawstring around my shoulders to get the maximum benefit. Washes well.

Bought this to provide extra warm for my 50 sleeping bag while camping in cooler temps. It was worthless and wouldn’t stay in place. We returned it

Great addition to a mummy bsg for cold weather conditions and offers versatility as a warm weather bag all by itself. Excellent light weight option.

The liner typically seems to add about 10-15 degrees to a sleeping bag rating. I'm in the Marmot eco-pro 15 degree bag, which has an EN rating of about 29F, and it has allowed me to use the bag on winter trips down to 15 degrees comfortably while wearing light long johns. I'm a warm sleeper. The liner is flexible, so it moves with you when you sleep and doesn't feel constricting. Like most liners it takes away the damp feeling in a bag and saves it from extra wear. I'd give it a 5 if it were made to absorb less smell, as a week in it without a wash/rinse allows one to smell the self quite well. All in all, great product, and on the lighter end for this type of item and amount of warmth provided. Used camping in Wyoming, Montana, Idaho, South and North Dakota, West Virginia, and Pennsylvania.

It's awesome. Buy it. This is a great bag for camping, traveling, in your bug out bag, or in the car, etc. Mine was black with a light blue trim around the opening, making it quick to orient. I'm 5'9", 185lbs, and was very comfortable in it. Fabric stretches a good bit. It's basically like a giant buff, and I'm guessing will prove to be pretty versatile.

Very small, lightweight, and super easy to pack. It's pretty thin and I'm often afraid I'm going to rip it while I sleep because I move around so much, but it has yet to. Adds a good deal of warmth to a sleeping bag. I found it helps to secure the hood cinch around my chest at night to keep it from getting tangled around my legs. Worth it I suppose.

I love this thing. I'm one of those girls that's always cold, and this liner really helps me out in that department. I think it really does add a lot of warmth to a sleeping bag if you're worried that your regular bag might not be quite enough. It packs down tiny and is pretty comfortable (large, soft-ish). The only weird thing about it is that it gets really static-y (gives you a little light show in your tent). Basically this liner a must-have for me. I'm very happy with this purchase.

I bought this to use as summer bag (when temps at nite are above 60), and to augment my 32 deg bag in early spring & late fall. Is very thin and provides zero padding. Is lite, but I have lite blanket I have used in the past that provides more warmth, comfort, versatility and can be wrapped over my shoulders while hiking or by the campfire. This product is just a thin liner and really didn't provide much additional warmth at nite by itself. In the 32 deg bag provided some extra warmth, but get same from extra pair of wool socks and sweater.

I used this on a 2-night trip in snowy conditions. It claims to add 15 degrees, and I'm not sure that it does. Maybe 7-10 degrees. Regardless of how much warmth it added, the comfort level was boosted immensely. I would compare it to having a sheet on your bed; doesn't add a ton of warmth compared to a comforter, but adds something special. And that something was awesome! It was great to have another layer to pull up over the shoulders, and to line the mummy hood with a soft layer.

This is a basic liner that buys you an few extra degrees and makes it easier to keep your bag clean. Its easy to clean, easy to pack and not very heavy. I've taken this into backcountry west virginia in october and it was honestly the most comfortable I have ever slept, though I have a multi part sleep kit to assure that.

Lightweight, packs down small enough (diameter of a Nalgene 32oz, half the hight) and super warm. I had to pull this out of my bag due to a temperature spike. I woke up in a sweat with my 32degree down back and the liner when the temp was around 57-59 degrees F. Would be great to use when temp drops below zero. Doesn't breathe to well. Fast drying, light weigh (i pack mine up with my bag in its stuff sack and don't notice the difference). I don't think I would use this as a warm weather sub for a sleeping bag. Not enough insulation. Overall, it does what it says.

Not sure how I went so many years without this liner. It makes your bag feel like you are sleeping on 1000 thread count sheets. Also keeps your bag clean from your sweat and grime. Packs tiny, so many uses. Just get it you'll love it.

No wonder so many great reviews!! What is better then a light weight multi function product?? Took this thing home and got in it on our bed just to get an idea of the weight and warmth!! I can see using this as light weight summer bag, for sure. But it will also serve to keep my regular bag clean from dirt and sweat... Also will through in my day pack for winter hikes. Just great all around!! Thanks, Sea to Summit!!!

I bought this bag primarily as a Summer bag when it's hot and humid. I have also taken it on some colder trips as a liner, but nothing below my typical comfort level in my bag, making it hard to comment on that.

I intended this as a summer bag and even though it got down into the upper 60s at night, with my clothes on this did the trick. I was hammock-tent sleeping with my 18 lb dog in there with me (it was raining) so I was worried about his claws tearing the very thin material. As such, I simply used it as a blanket and as long as it stayed on top of me, it did the trick well. Will definately take it on winter trips as a proper liner.

The fabric is very soft and comfortable...unless you are sunburned or have dry, cracked skin from alpine days. The fleece sticks to sunburn, unlike silk (ouch). Aside from that, it was warm and roomy enough I didn't feel too confined while sleeping in it(I'm 5'5"). Quick and easy to pack. Doesn't add too much warmth, maybe 10 degrees max, but that isn't what I purchased it for. Breathes really well!

bought it for a backpacking trip around the Minarets in the Ansel Adams Wilderness. kept my sleeping bag clean. And it actually wasn't very cold so I slept in just the liner with my sleeping bag open. very very comfortable.

I bought the liner for a cold winter hike/backpacking trip in the Shenandoah Mountains near Old Rag in VA. Temps that night bottomed out at 18 degrees. I have a zero degree down filled Kelty bag which works well, but it isn't as high end as some other bags as there is some temp slippage around the bottom of the bag. I bought the liner in hopes of overcoming that issue and adding additional warmth, which it absolutely did. The texture alone makes the experience very comfortable and added warmth beyond what I had expected to my entire bag. I have a long mummy bag and the 7 foot liner even reached over my head and face which added additional comfort and heat loss avoidance. I was comfortable all night and slept well. I will be using the liner as my sleeping instrument this summer during a 50-60 miler in the same area of that park. Overall, a great purchase/investment which I absolutely recommend.

I bought this to add warmth to my 20degree bag. I sleep pretty warm, but this hasn't done anything to add warmth. Good for keeping the bag clean, but that's about it for me. I've had it for about a year.

This liner was very warm! Only problem is when i twisted and turned in my sleeping bag it shifted all around twisting around my body and constricting my movement. The headloop also started to cover my face. Still great to have instead of heavy layered Army sleeping system. And also an option for the summer. Thin enough to allow breathing when wearing alone.

The best thing about this liner is the ability to pack it away easily. You can roll, stuff, push or do just about anything you want to it and it will fit in the storage bag. Its not a very think liner and I don't know if the 10 degrees it claims to add is always true. That being said, I always bring it with on any trip I go on. Very easy to clean and so far is very durable. I really enjoying using this during long trips when i get greasy. It helps to keep the bag clean. I can also use this alone on nights around 55 degrees.

Bought this for the second half of my thru-hike of the AT when the weather got hotter and my sleeping bag was too much. Didn't expect to love it as much as I do! It's cozy, cool, and protects my toes from the mice in the shelters lol. I love that it stretches bc I tend to move a lot in my sleep. Best product ever!

Certainly not what I expected. The liner could benefit from a zipper, getting in it isn't easy...especially if you're a bigger or taller person. Personally feel it's about $30 overpriced for what you get, not worth the money and found it to be more of a hindrance. Will be returning the two I bought from REI.

Took it out right after purchasing and will definitely be returning. My sleeping bag should be able to tolerate cold night, but I run cold so I figured the liner would help. Honestly, I can't really say it made a difference. I still woke up with frozen toes.

I picked this liner up last minute before hiking the divide in early September. The temps were below freezing and I woke up to 4" of Unexpected snow! This liner gave me that little extra I needed to comfortably make it through the night.

I've used this many times in my 30 degree mummy bag. first off it is extremely hard to get into in the dark and out of. then the fabric is so thin and worthless that you can see through it. in 25 degree weather wearing an under armour suit and wool socks I was freazing. this was one of my worst purchases ever!

feels like a very soft jersey material ... comfortable. used this during my travels to uganda as a sheet as well as a liner in my sleeping bag while camping. looking forward to using it on my backpacking trip in two weeks! got into my bag with cold feet & legs and within minutes i was warm. used this with my +15 bag. if you have to get out of ur bag in the middle of the night, it's easy to find your way back into the bag and into the liner ... the blue cording makes it easy to find. enjoy!

after being uncomfortably cold on my first two backpacking trips this season, I stopped by and picked one of these up. It cured it. I actually got too warm, but I bring this every time just in case!

This bag liner save my rear on many cold night on JMT. The only problem is getting in and out of it in sleeping bag. Very light and material is very comfortable! Very good investment!

Bought this for a trek to add warmth to my bag and it worked great! It cleans easy and dries fast. I have used this on a few trip now and is still holding up like new.

This liner is way too thin to use as a summer bag alone. I used it in a 70 degree room at night and still had to throw a blanket on top of it to keep warm. There is no way I would use this in the field alone if there was even the slightest breeze. You can hold the liner to the light and see through it. It might have some cold weather applications, but it is most definitely NOT a good alternative to a summer bag.

Bought it for a week on the AT. Temps down to the 30’s. Works better than my electric blanket at home. Don’t hit the trail without one

I have done a lot of research for the past 2 months on what bag liner I should buy. I was going back and fourth between this liner and a silk liner. I bought this one based on the amount of reviews and how many were positive.

I wasn't expecting something so thin - once I saw it I anticipated that it wouldn't be as warm as it was supposed to be. I tried it out first at home, with the heat turned down, under a comforter I knew would not be warm on its own - this liner kept me warm and toasty, didn't make me feel confined, in fact I hardly knew it was there. I'm guessing this will make up for my thirty degree bag not really being warm as advertised, and I'm glad I picked this up.

I bought this to extend the life of my down sleeping bag, which is about 20 years old. This is just what the doctor ordered. My 40-degree down bag was working more like a 60-degree down bag in my hammock sleep system. I've used this liner twice now and slept more comfortably than ever.

I am cold-natured and after nearly freezing to death on a previous winter campout, I bought this liner. It was light and easy to pack and allowed me to cover my face without being smothered. (I need my nose to be warm or I am miserable!!) Will be trying it this weekend for a summer campout without my sleeping bag. Will pair it with a blanket to cut down weight and bulk in my pack. Good investment for those who needed additional warmth!!

This is one item I would never leave home without. Whether I am camping at home in Bermuda or in the Andes of Peru to the Himalayas of Northern India, this is the most precious item in my pack! In warm weather camping, I don't even bring my sleeping bag, I only use this! In really cold weather, like on the Auli-Kuari Pass in India, this item was an absolute life-saver. This is a not-to-leave-home piece of equipment!!! BUY IT NOW!!!

will keep your bag clean but adds no warmth

I've had this liner for quite some time. I used it exclusively on a two year global trip to add warmth to chilly train sleeper cars, hostels and guest houses with too thin sheets, and the occasional summer night outdoors. By no means is this to be considered a sleeping bag substitute. But, if you want a lightweight boost to flip a night's sleep from being a touch too cold to just being right, this a great option.

I got this to extend the life of me sleeping bag, as it is 10 year old. It definately changed my warmth and comfort level for fall backpacking. It is super soft and light. It stuffed right ito my sleeping bag sackso no extra stuff sack to consider. It was is super cozy just to sit in when chilly in the mornings when you just can't get motivated to break down camp. Great late/early season camping extender.

Despite all the reviews and comments this little liner is awesome. One night at Philmont at 9k with 10 mphs winds and 32-F temps I slept in my trusty 12yr old down bag without the liner. Next day same condtions applied but with the liner and it really kept the heat in and I could feel the differnce. Standard equipment for me and my crew during October when we backpack Philmont and need some warmth

I bought this as an insulator for my +15 sleeping bag. I wanted a lightweight cover for slightly cool nights when the sleeping bag is too much. I will be using this in the sleeping bag all winter long as I work in an outdoor wilderness education organization. So far so good, but the 10 and 20 degree weather not yet happened.

I have a 20 degree MH down bag. We went out for a trip in the Smokies, temps expected around 10 degrees. So, I figure this would get me there, especially wearing wool long underwear. It dropped into single digits.

I want to start off by saying this is probably a combination Bag/Liner issue, not simply the liner. I bought two of these about 2 weeks ago for my son and I for a Boy Scout trip to Camp Highroad in Middleburg, VA. The weather was great during the day (mid 50s) but at night it started raining and the temperature dropped into the 30s. I was using a 20 degree Outdoor Vitals Summit down bag with this liner, along with a Sea to Summit air mattress. I was wearing long underwear, heavy sweatpants, cotton hoodie, turtleneck, beanie and smart wool socks. I was pretty well layered. I was fine at first but woke up around 3:00 AM and I was cold. Pulled sleeping bag hood over my head and zipped myself in to stay warm. I am sure this was a combination bag/liner issue. I plan to buy the heavier liner to see if that works better for cold weather camping, I'm sure this is fine for late spring and early fall but for late fall and winter camping it wasn't enough with a 20 degree bag.

Thought this would come with a zipper, but it doesn't. Also, it appears too thin to be of any real value, especially for the price. Returning them without using them. We have fleece liners from Walmart that are great, but was looking for something smaller and lighter, but not this light!

I liked this liner as an addition to my +20F sleeping bag, which I always get cold while using. I recently took this liner camping in Yellowstone and it definitely helped warm things up a little to the point where I was chilly, not cold. I am always cold-natured though. I also used just the liner by itself when camping in northern missouri and it worked great.

Just looking at it the first time I never thought it would at any warmth to my bag. But little did I know that it most likely added 10-15 degrees like it advertises. It is super thin and almost fleece-like which makes it ultra comfortable! It's also very compact and lightweight which means I'll be taking it on every backpacking trip forever!

I don't know if it adds 15 degrees like it claims but it certainly adds significant warmth to a sleeping bag and it keeps your bag cleaner. Even though the fabric feels like you will tear it easily it has held up nicely to my abuse. Large enough to fit nearly everyone. All of my friends own their own reactor liners now after trying mine.

Comfortable, spacious and adds warmth. Machine washable is key. Too new to know how many washes it will tolerate. Only negative is the zipper on your bag becomes worthless because this doesn't let you in and out through a side. I keep it in my bag so I don't take up room in my pack. Bag rolls up and stiffs as if it wasn't even there.

I purchased that Sea to Summit Thermolite to use with my hammock system and it has been a very good purchase. Not only does it help to keep my Top Quilt clean it also helps trap heat helping to make my hammock sleeping an enjoyable experience. So far I have used it down to 17 degrees with my 20 degree Top Quilt and I felt quite toasty.

It's small, light, and warm. Easy to wash and doesn't show signs of wear for it. I use it alone sometimes and it makes it so I don't have to go buy a heavy sleeping bag for places that actually get cold. I don't find myself sweating or feeling uncomfortable using it and I haven't noticed it holding smells.

I used this snow camping this week in Colorado, and the temperatures were between 0 and 10 every night. I am an extremely cold sleeper, and my 15 degree down bag got wet, but I was still very toasty in this thing! It is really small and light. I am so pleased with this liner. I will take it on every trip!

Very durable. I was afraid I was going to tear through this on several occasions during sleep, but it held up. I read a review that someone used it in place of their sleeping bag, so I tried it one night on a summer backpacking trip in the Badlands (SD). Don't do it unless you are a warm sleeper.

Extremly good warmth to weight ratio. Unlike most fleece liners fabric streches with you when you move around. Never used in in super cold weather, but works well, for me, in tempartures of 30 degrees and above. Packs down super small and is very light weight. Excellent choice for a liner.

I used this last summer in the Sierra's and loved it. Since I was sleeping in my bag every night I was mainly using it to keep my bag clean (which it did) but I found it to provide that extra added warmth/comfort. It packs small, easy to wash and stretches really well so it doesn't rip.

I bought this product to use with my 30 deg rated mummy style sleeping bag. I used it on a recent hiking trip in the NC mountains and the temps dropped below 22 F and I was very comfortable. I sleep in a hammock with a R3 pad underneath my bag. With the above system I was plenty warm.

My wife and I bought these for winter camping. We very comfortably hammock camped in 30 degree temps with these inside our 20 degree bags. All the grime you collect during the day will transfer to this instead of your bag so you can throw this into the washing machine when you get home.

Every bit as warm as my fleece liner, maybe warmer. Packs down to about 1/20 of the size. Super small and light. I may get the Xtreme version for my wife since she sleeps a lot colder than I do. I plan to use it as my lone cover in the sweltering summer months in the Carolinas.

Used this on an Alaskan moose hunt. I used it with a -25 degree bag. Temps got down to about 20 degrees at nite. I was sweating. My partner had a 20 degree bag and he was freezing first night. I let him use it the rest of the hunt and he was warm. I recommend this liner.

OK so I got this "liner" bag as a sleeping bag when I took my good bag to cleaners and cause they messed up I was not able to get it back in time for my trip. As it was not going to be too cold I guessed that this along with my layers would suffice for the weather. I did not want to spend a grip getting another full-on bag (assuming I would eventually get mine back from the cleaners, but that is a different thing) so I decided to take a chance on this one.

Bought these for the wife and kids for a trip out west. When it was very hot these were comfortable to sleep in. When we started to go a bit further north then they needed some additional back up. Make ideal sleeping bag liners for the colder weather.

this thing is great, i first bought it thinking that it might be a flop, but was won over by the weight; and i thought i can test it out and maybe return it. after i usd it once or twice i found that this is great on its own and as a liner.

Bought two of these to give us a little extra warmth on the cold nights as well as to keep our bags clean. These worked very well for this. They breathe, are comfortable, large enough for a 6'2" 200lb man, and are all around durable.

Light weight and compact. Provided geat additional warmth without the need to purchase an additional pricey bag for the few trips I take when it gets that cold. Blooming forward to taking it solo on summer trips

I was glad I brought it on a recent backpacking trip for the extra warmth. I'm a little bit of a wild sleeper, so I did get a little tangled. The material does not breathe well.

I purchased a Big Agnes Horse Thief sleeping bag, and figured I would combine it with a Reactor liner when the tempatures dropped. This liner is warm, comfortable and warm!

Great product to have if the weather decides to dip lower than your sleeping bags temp rating. I have used it on many occasions and it works great. No complaints here.

Purchased this to add a little extra warmth to my Summer bag. It is a great way to create a layer system for your sleeping bag set.

I bought this to take to Machu Picchu since I was renting a sleeping bag from the outfitter. I was toasty warm the entire time!

Great add to my backpack; added warmth to sleeping bag or by itself on top of sleeping bag, with little added weight.