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Sleep warmer and more comfortably thanks to the soft Sea To Summit Reactor Thermolite Sleeping Bag Liner.

The Sea To Summit Reactor Thermolite Sleeping Bag Liner weighs only 9.2 ounces, adds up to 15 degrees to your sleeping bag's warmth, and packs to a tiny 3 x 5 inches. The key to this Sea To Summit sleeping bag liner's excellent stats is warm, breathable hollow-fiber Thermolite material. This sleeping bag liner weighs less and packs smaller than a comparable fleece liner, which makes it ideal for both backpacking and nights in the hostel.

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Review Summary
2 4
5 3
4 2
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Sea To Summit Reactor Thermolite Sleeping Bag Liner

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Size Comparison

Size Comparison

Posted on

This liner packs down in size somewhere between a Campbells soup can, and a nalgene. It's slightly larger than a Campbell's Chunky soup can.

does this liner have tabs on it to attach...

Posted on

does this liner have tabs on it to attach it into a sleeping bag like the big agnes'?

Best Answer Responded on

To the best of my knowledge this liner doesnt have anything to snap, tie, or connect the liner into another bag. However, I haven't found it to be a problem on any of the multiple times I have used it, even with my slick poly-lined bag. To be perfectly clear, the liner stayed on where it should + kept me warm - no bunching, no deforming.

I think any kind of connection would just be cumbersome + pointless considering there isnt anywhere for the liner to actually go once its between you and the other bag. So if that is what is the only thing holding you back from buying this, I would consider it to be a non-issue + snag this portable incubator.

3 5

Thermolite Reactor

I bought a couple of these for my son and I for a high country trip. I felt that it worked quite well. Not sure it was 15 degrees worth of warmth but did add warmth for very little weight.

4 5


I brought and used this liner on a month-long trip in the Sierra Nevadas. It was warm but I don't think it added 15 degrees to my bag (not that I needed it to, I use a 25 degree bag). For me, this is a comfort item. It's like having cozy sheets inside your sleeping bag. I used to stay comfortable and to keep my bag a little cleaner. For my purposes, it worked great. I think it's a good liner but not necessarily any better than any other liner out there.

4 5

Warmer than a can of soup

I threw this in my pack for my latest backpacking trip. I have a 45 Deg bag and didn't have the coin to go buy a 30 Deg bag for my trip to Yosemite. Obviously this was way cheaper than buying a new down sleeping bag (hello Christmas present), but it still did the trick! I woke up cold my first night, rummaged around in the dark, grabbed this liner and quickly slid into it. I didn't go to sleep without it the rest of the trip. It's really comfy too, feels a lot better against the skin than my sleeping bag.

Like most have said - it is thin, you can see through it. That didn't seem to stop it from adding that extra bit of warmth I needed. I would've froze my cajones off if it weren't for this thing. I didn't have any trouble fitting it in the stuff sack it came it, just stuff it in there! Don't bother trying to fold and roll it up - you'll have trouble getting it back in that way. It packs down about the size of a can of soup.

For me it was definitely worth the $50 to have that extra bit or warmth. It'll probably find its way into my pack whenever I'm going on trips and I'm not entirely sure of just how chilly the nights will be. It's a great addition for those "just in case" excursions.

5 5

thought I needed a new bag, but....

I have a 30 degree bag + as with most bags, this number is more or less irrelevant - temps in the 40s left me frozen, warmer temperatures left waking up sweating.

SOLUTION - this bag liner. It can be used stand alone as a summer bag or inserted as the liner in colder months.

It does look as if its rather wimpy (can see thru it), but seems to be standing up to the (ab)use its getting + dries quickly if it happens to get wet. The material is soft against the skin which is a welcome relief to most bags.

The size, weight, + ease of packing of this thing are great characteristics too. Even if you don't end up using it, you sacrifice the size of a soup can + much less weight.

4 5

Pretty dang good

I love this bag liner. Take it on every trip with me just in case it gets cold. I used this one night in15 degrees and my bag was a 40. I was never cold. In fact it was one of the best sleeping camp nights I've ever had.

Only gave it a four because I wish you could UAE it alone in cold weather. I've triedto use it in 60 by itself and got pretty chilly.

Bottom Line: if your looking for a great bag liner, look no further, you will never beat this one for weight, compactness, and warmth. It's the trifecta.

How do you wash this liner?

Posted on

How do you wash this liner?

Responded on

Toss it into your machine for a cold gentle wash and then hang dry it (it will dry quick without a dryer but a quick tumble with low heat shouldn't hurt it at all).

3 5

I expected a bit more.

I don't see how this really adds 15 degrees of warmth, though I still use it as part of my down system. Like any other liner, it helps keep the sleeping bag clean, packs small, and weighs little. Soft material feels great. It is honestly so thin that you can see through it, though I took it to the smokey's in TN this summer and used it alone as my sleeping bag.

3 5

Waiting for a better solution

This fabric liner is effective -- though doesn't really add 15 degrees of comfort to a 3 season bag. The stuff sack doesn't compress, and is just big enough for the sack. In my experience, it is way too much work to get it back inside; I just add it to the compression sack that I use for the sleeping bag. It does look like it would work nicely as a stand-alone bag in the hot weather.

5 5

Worth the money

I bought this liner after reading some reviews about it and became instantly skeptical when I saw how thin the liner is (as someone said, you can see through it) but I was impressed by the liner. It doesn't give the 15 degrees it says (10 is more accurate) but it can't be beat for comfort or packability

4 5

works ok

nice to use alone in warm weather..also packs up small and is very light

4 5

pretty nice

I've used this liner for awhile now, and it is definitely nice to have on the cold nights. I agree that it doesn't quite add 15, more like 10 degrees to your bag. It also feels nice next to your skin and adds quite a bit of comfort to your bag.

3 5

works, but I'm not convinced it's the best

Essentially this is a giant polyester sock. It feels quite thin (you can
see through it if you hold it up to light). I don't know about 15
degrees, but it did add a noticeable amount of warmth to my 30 degree
bag on a cold night. The drawstring comes out on the left by default but
with a little effort I moved it to the right. I didn't feel like it
inhibited motion in my sleeping bag, and it was relatively easy to get
in and out of.
It may be a little heavy (and expensive) for what it does. After all, it
won't be as efficient as down for its weight. If you bring it and don't
need it, at least it makes a decent pillow.