Sea to Summit - Thermolite Reactor Fleece Liner - Regular

Category: Sleeping Bags

It's ok I guess. I am honestly torn on whether to recommend it or not. I suppose if you want to use it only as a liner then it would be great for that purpose.



I'd like clarification on the additional warmth of two liners (Sea to Summit Thermolite Reactor Fleece Liner -and- Sea to Summit Thermolite Reactor Extreme Mummy Bag Liner. I want to buy the warmest liner available. Which will "add the most warmth?"

The Sea to Summit Thermolite Reactor Fleece Liner adds approximately 30 degrees of additional warmth to your sleeping bag. The Sea to Summit Thermolite Reactor Extreme adds about 25 degrees of additional warmth.


I'm between this liner & the Thermolite Reactor Extreme Liner for additional warmth on a backpacking trip in Chile. Is the fleece liner worth the extra weight? I want to be sure that there's added warmth and the thermolite seems to have mixed reviews.

​​The fleece liner will provide more additional warmth then the Thermolite Extreme. The extra weight might be worth the warmth gained depending on how you sleep (warm or cold).


Currently using the Sea to Summit Reactor Plus with a Marmot Nanowave 45. Would this be able to get me below 10 degrees? Would I be too warm when temperatures are in the 30s if I vented my bag?

This fleece liner will add approximately 14 degrees of warmth to your Nanowave bag. This would turn your Nanowave into 31 degree sleeping bag. If you do become too warm, you can vent your sleeping bag by opening the bottom zipper or remove the liner.


Would adding this liner to a 21 degree woman's bag rival a 0 degree woman's bag in terms of warmth? 

Sea to Summit does not provide exact degree increase for how much extra warmth this liner will provide. They say that it will upgrade your sleeping bag by a season. So if you have a 3-season sleeping bag, this would make it a 4-season.


I am curious why the size listed is only 28" wide whereas the regular Thermolite liners (no-fleece_ are 35" wide? Is this dimension accurate? Is it snug to get inside? Seems to be a huge difference in width.

The width listed is correct; it is 28" wide. It is designed to be a mummy style liner so it is snug fitting, which does aid in warmth.


Where is the zipper located? Side or middle? I ask because I'll be ordering a USMC 3 Season sleep system and the zipper on it goes down the middle.

The zipper on the Thermolite Reactor Fleece Liner is on the left side of the bag.


is this warmer than the reactoer extreme?

Yes, this is Sea to Summit's warmest liner in their Reactor series.


What is the best use of this product? Can it replace a standart sleeping bag?

The Thermolite Reactor Fleece Liner can best be used to extend the warmth of your sleeping bag or it can double as a stand-alone summer bag. It would only be an acceptable replacement for a full sleeping bag on very warm summer nights.

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