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Rated 5 out of 5 by from Best thing ever! I purchased this to give me some extra warmth (I run cold) in Patagonia, and I am so glad I did! First, I was surprised by how thin and soft it is. Really soft. I used it a few times while hanging out on the couch at home, and it truly does keep you warm. If it's really cold, you need to cinch it up properly (I rarely did) and you'll be roasting in no time. I ended up taking it on the long flights with me, and using it as an airplane blanket. Frankly, I also planned to use it as a shawl if I needed it while hanging out in the evenings. It's amazing. I'm not putting it away with the camping gear, I'm keeping it handy as a spare blanket at night to go star gazing!
Date published: 2015-03-31
Rated 4 out of 5 by from Compact and versatile I bought this bag for several reasons, but primarly for a lightweight and warm weather bag. I'm in NC and do most camping in NC and it's warm here most of the year. I bought this bag/liner and have so far only used it alone. And that's what I wanted it for. It's cozy to sleep in and just right for warm weather camping. In "cool" weather, I've used it with a space blanket over it and was fine too. I haven't yet tried as a bag liner, but based on its solo performace I'm sure it will add a few deg of warmth to my mummy bag. I also keep it in a survival pack in my trunk when not camping.
Date published: 2012-10-15
Rated 5 out of 5 by from a must-have travel item I have only good things to say about this liner! I'm a small girl who gets cold easily and this is a wonderful item to own if you camp or travel. It only weighs a few ounces, is easily stashed in its own little stuff sack, and has so many uses. I've actually pulled it out on international flights (like I said, I'm always cold) and I've used it in my bed when staying in hostels or hotels with questionable cleanliness. It was perfect when backpacking in Japan where temps reached 110 - something to cover myself but not get overheated. Washing/drying is a breeze, too. Highly recommended!
Date published: 2010-05-22
Rated 5 out of 5 by from Magical I join the ranks of satisfied reviewers. Writing this review on behalf of my sister... we trekked for 3 months in a Himalayan winter that spilled into summer. Since I joined the trek late and had heard my sister was struggling with the cold, I brought her this liner to warm up her sleeping bag. I haven't seen her so in love with a fabric since her childhood blankie. She even opted to use it once we returned to town and checked into a guesthouse. I was skeptical to buy this at first because of the price, but seriously, what's in this thing? Magic? Worth the dough if you're into cozy factor.
Date published: 2009-09-28
Rated 4 out of 5 by from roasty toasty i've only had one opportunity to use this since i just purchased it, but so far, so good. we camped in 20 degree weather and my husband had to shed his after getting too warm (we also have 0 degree bags, but they are ~15 years old) so i doubled up and had the best camp sleep ever. he would likely leave a less glowing review since he is a human radiator and also like to turn cartwheels in his sleep and found the liner a bit too confining. typically, we zip our bags together which gives him a bit more room to kick me in his sleep, however, since these are super light, there are no zippers to combine them so he was additionally confined to his own sleeping bag (probably another reason i slept so good!). short story long - i loved the liner, but he would probably have a different story.
Date published: 2013-01-31
Rated 4 out of 5 by from Great purchase! I recently took a trip to Yellowstone and did some backcountry camping. The temperatures got down to the mid/low thirties overnight and I knew from previous (and uncomfortable) experience that my sleeping bag wouldn't keep me warm enough. I purchased this liner to supplement my sleeping bag and it totally worth the money. It's very thin and lightweight so I was concerned about its effectiveness, but I was incredibly comfortable and warm all night. The fabric is also very soft and cozy and added minimal weight to my pack.
Date published: 2013-09-19
Rated 5 out of 5 by from Cold to comfortable Brought this just in case for my first outing of the year this April, Herman Creek in the Gorge. Still pretty cold at night and snow at 3200 ft. I have a 20 degree bag and I was at the edge of being cold the first night at a lower elevation, but managed to stay warm. The second night was a bit higher and colder and I was having trouble falling asleep so I broke out the Thermolite bag liner. It's pretty thin, didn't really think it would do much but it did. It took the edge off, I warmed right up and fell fast asleep. In my opinion it's a great way to ad versatility and warmth to your sleep system without having to purchase another sleeping bag. Glad I had it with me. By the way, get in the liner first and then slide into your sleeping bag. This technique seemed to work well.
Date published: 2013-05-24
Rated 5 out of 5 by from Works [Better] than Advertised Field tested this liner paired with a Mountain Hardwear 45 deg UL bag atop Mt. Kimball in Tucson's Santa Catalina Mountain Range. Temperatures dropped to 30 deg F at night, and this liner kept me warm and toasty. (So toasty, in fact, that I actually took the liner out around 2 AM!) This liner can also be used to shave a few ounces off your carry weight as you can use a lighter, cooler bag rather than a heavier, warmer bag. (Or, you can carry this and this alone in warm temperatures!)
Date published: 2014-11-04
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Questions & Answers

On a multi-night / multi-campsite hike, I'm wondering if I should keep the liner and bag separate or is it ok to roll them up together before placing them in the compression sack before heading out to the next campsite?

Asked by: m squared
​The liner and bag can be left together when using a compression sack.
Answered by: REIservice
Date published: 2018-02-16

Is this product machine washable?

Asked by: Ohio Runner-skier
From Sea to Summit: "...the liners can be washed in a home washing machine using normal detergent (referred to as laundry ‘soap’). If you are using a top-loader washing machine, we would strongly suggest putting the liner inside a pillow case to prevent the impeller (the spiral plastic rotating column in the drum of the machine) possibly snagging the draw cord. A front-loader is much gentler on your gear, and this step is unnecessary. In either case, use the delicates or gentle cycle. Fabric softener will decrease the wicking performance of the fabric, and should be avoided. Do not dry the liner in a dryer; excessive heat can damage the fabric – air-drying is the way to go."
Answered by: REIservice
Date published: 2018-02-15

How long is this liner? Is it long enough for someone who is 6'5"?

Asked by: tallKT
The Reactor Thermolite Mummy Bag Liner measures 7 feet in length.
Answered by: REIservice
Date published: 2017-06-02

How does the entry work? Does it have any type of side entry zipper or

Asked by: bruce K
This bag has a wide entry at the top of the bag and draw cord hood.
Answered by: REIservice
Date published: 2017-05-01

I have the Sea to Summit Expander bag liner but am looking for a warmer option for colder nights (so I can take my light sleeping bag). Does this liner stretch as well?

Asked by: biggster
​This liner does offer some stretch, but not as much as the Expander.
Answered by: REIservice
Date published: 2017-08-17

I'm getting into the practice of hammock camping and found that 55 degrees F is my limit before my back begins to feel the cold through my sleeping bag. I'm researching the underquilt options but came across this as well. Could this work instead?

Asked by: AndyN
​This bag liner is a great choice for adding an additional 15 degrees of warmth to your sleeping bag.
Answered by: REIservice
Date published: 2017-12-25
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