I absolutely love my Sea to summit camping supplies in reactor fleece, sleeping bag liner color orange mummy with drawcord. It keeps you warm in temperatures below 0°. It is so comfortable and yes, it really does. Keep you warm extremely warm. I would definitely recommend this product. I would definitely purchase this product again. 

Adds that missing layer of comfort

Got to take this out a few times now, including a week up in the ADK’s for the eclipse after blizzard like conditions. I won’t sleep without some form of liner so when I saw the updated designs, I knew I had to get one. Really helps keep your core body temp when changing in/out of camp clothes for the day/night. I really like the micro grid fleeece design and feel. Definitely adds a good bit of warmth and a ton of comfort that can lack when laying in a sleeping bag. It’s been a really convenient for hammock use too. I like this one so much I bought the Extreme for when it warms up a bit.

Best investment

The Sea to Summit Reactor Fleece Sleeping Bag Liner is a fantastic product and a much needed one for camping. It provides extra warmth on chilly nights, extending the usability of sleeping bag into colder seasons. The fleece material is so soft and cozy. it’s lightweight and packs down making it easy to transport. I used it when I went camping last weekend and i will say , this will be a best investment for those who go camping. Love mine.

Highly satisfied

Really satisfied with the feel of the material, the durability, and effectiveness of the bag liner. I got the extreme version because I wanted to be able to pair it with my 20° bag and get more range and extend its life. I also planned to use the bag liner as a hot summer night sleeping bag. It’s also much easier to wash than a sleeping bag. So it’s nice to use on the trip. Turns out my favorite use for it is as a summer bag. It’s very small when packed compared to a sleeping bag and works well to keep you comfortable on a backpacking or bike-packing trip on warm nights

I've used STS liners as

I've used STS liners as part of my sleep systems for years. Bought a Reactor recently to help beef up an older synthetic bag that has lost some of it's loft. Was impressed with increased warmth but, after experimenting, am feeling it added considerably to the bag's capacity but well south of 30 degrees. Also, the material is quite "sticky" so getting into the liner while wearing inner or mid layers, was a bit of a wrestle. That said, once situated, the liner felt super cushy and seemed to take up minimal space in the bag. I do a lot of moving around while sleeping and did not notice the liner tangling while flipping around. Here in NE, we get wild temp fluctuations so am particularly excited to use this liner as part of a super flexible system, on it's own, while ... MoreI've used STS liners as part of my sleep systems for years. Bought a Reactor recently to help beef up an older synthetic bag that has lost some of it's loft. Was impressed with increased warmth but, after experimenting, am feeling it added considerably to the bag's capacity but well south of 30 degrees. Also, the material is quite "sticky" so getting into the liner while wearing inner or mid layers, was a bit of a wrestle. That said, once situated, the liner felt super cushy and seemed to take up minimal space in the bag. I do a lot of moving around while sleeping and did not notice the liner tangling while flipping around. Here in NE, we get wild temp fluctuations so am particularly excited to use this liner as part of a super flexible system, on it's own, while covered with a sleeping bag (as a blanket) or inside a bag. Will certainly enable me to cut down on the number of sleeping bags I have had to stock.

Lightweight addition to camping gear

I received this product complimentary in exchange for an honest review. As described, this is not a sleeping bag per se but rather a liner for a sleeping bag. It is not waterproof. It would provide another layer of warmth. It is thin and lightweight but the material seems thermal.

Mummy dearest

Received this fleece-lined sleeping bag and it's been a game-changer for camping or staying over at a friend or family member’s house. It's cozy, lightweight, and tough enough for any situation. I love how it cocoons you and makes you feel nice and toasty. Worth every penny for the comfort and versatility it brings. Comes with a great compact travel bag too. Highly recommend!

The Sleeping Bag Season Extender I Needed

Huge huge fan of this liner. I have a three-season sleeping bag, but in the shoulder seasons I find myself needing a lot of extra layers and running colder. This liner totally changed the game for me! Took my sleeping bag from doable to super warm on a November camping trip, and allowed me to ditch sleeping with a puffy/hat/million layers of clothing for a much better sleep.

Very warm, nice and soft, but legs felt restricted

Used this for the first time last week in Fall Creek Falls and the low overnight was about 31 or so. Paired with my new BA Anthracite 20 bag (also first time use). I do NOT like the cold and I consider lows in the 30s as the absolute lowest overnight temp I would choose to camp in. I was pleasantly toasty all night - never too hot - felt great! The liner is soft. My only complaint is that my legs and feet felt very restricted. The second night was around 45 or so degrees so I used the bag alone without the liner and discovered the restriction I felt the first night was due to the liner - not the mummy shaped sleeping bag. Perhaps some kind of stretchy material could be added to this liner from the hips down - even better if that fabric was “slick”. If that could be ... MoreUsed this for the first time last week in Fall Creek Falls and the low overnight was about 31 or so. Paired with my new BA Anthracite 20 bag (also first time use). I do NOT like the cold and I consider lows in the 30s as the absolute lowest overnight temp I would choose to camp in. I was pleasantly toasty all night - never too hot - felt great! The liner is soft. My only complaint is that my legs and feet felt very restricted. The second night was around 45 or so degrees so I used the bag alone without the liner and discovered the restriction I felt the first night was due to the liner - not the mummy shaped sleeping bag. Perhaps some kind of stretchy material could be added to this liner from the hips down - even better if that fabric was “slick”. If that could be woven into the existing fabric to retain the warmth but allow more freedom of movement without it ‘grabbing’ onto your legs/PJ bottoms/socks that would be truly amazing. Giving this four stars overall due to the restriction I felt (others may not) - but would give it five stars for warmth without burning me up.

Warmer but not 32' warmer for this cold sleeper

I intentionally took a sleeping bag not warm enough for my camping trip to test the liner. The liner was soft and I liked the zipper and hood. It ended up colder than forecast so I was thankful for a back up down blanket. The liner did make the sleeping bag warmer, but being a cold sleeper, it did not increase the warmth by 32', perhaps 10' for me. I still love the liner and will simply add it to a better rated bag next time.