Sea To Summit Reactor Extreme

I bought this liner for winter solo backpacking to beef up my 15F Wenger Rhone 800-fill down bag. The bag is very warm for a 15F but I tend to be a very cold sleeper, so I need to have something that beefs up my temperature rating for nights below 20. I used it on a humid night that got down to about 15 or 10, and stayed very warm with only a thin base layer on. Without the liner I would have been cold. The improvement in temperature rating I would put at about 15 degrees, realistically. Be wary of people who say it does not work, especially if they do not know the limits of their sleeping bag well or are using insufficient ground insulation. For winter backpacking I use a R-5 big Agnes Q-Core with a closed-cell ThermaRest foam mattress underneath for added insulation. No sleeping bag will protect you from the cold ground. The liner is comfortable, easy to use, and packs up small. Also plenty long and roomy enough for me, I am 6'2" plus and 220 lbs. Overall very happy. Don't really expect the liner to convert your bag into a full-on winter bag, those have special face baffles and other jazz to keep you warmer, but on a budget it will keep you warm below your sleeping bag's temperature rating.

This is a great product. We got my wife one because she is always cold. She has a nice REI bag but just sleeps cold sometimes. She has been a huge fan of this and it has kept her warm.
I got myself one after because she liked it. I sleep warm generally so I usually carry it when we go camping or backpacking but never really had to use it. It's very lightweight and easy to pack. For its size it makes it ideal for many different situations. I have the North face Cat's Meow bag, went on a camping trip a few days ago in Colorado. Colorado camping in November can get cold up in the mountains. We were just above the 0 degree mark with wind pounding away at around 9,300ft elevation. Once I got warmed up in my sleeping bag it actually got a little too warm to where I unzipped part of my bag about 3am. It worked great. I think as long as you have a good base bag this will help, if you have a cheap bag not much is going to work for you. For the weight and warmth this thing offers I have already recommended it to several people.

I bought this to replace my sleeping bag on warm (>60°F) trips due to its extreme compactness and lightness. Used it thus on one trip. and learned that the slightest breeze (<5mph) is enough to negate its value. But if you cover yourself with a tent fly or something similar, it works like a charm (I was in a relatively open hammock).

I became suspect of the 25°F rating. I have a 15°F bag that I've tested successfully for its rating. Last night I spent the night in the bag and liner in ~0°F environment (digital thermometer said -3.2°F). It was slightly chilly - but for full disclosure, the cold was coming up through my mattress. Putting on thermals did the trick. I'd say an optimistic rating is closer to 15°F. It works, and while probably not quite as warm as the manufacturer's rating, it also is nice to have an easily-washable liner.

I got this liner almost on a whim but have since really used the heck out of it. In Summer is makes a great great light sleeping system. In Winter with temps dropping to single digits where I live I include it in my zero back for that extra warmth that makes it so much easier to deal with. I typically will pull the sack up about chest high so i have some foot wiggle room in it and stay very very warm. It is one product that truly does help the rating on your sleeping back improve. The regular bag liner works great with Big Agnes sleep system matress bags. I also use this as a tiny sleeping bag during the summer months when you really dont need one but in higher elevations it gets a bit of night chill on. I found this to be an excellent product.

I have only used product in a cold condition, but feel after using it that it is so sheer and lightweight that it seems perfect for summer as a "light" bag.

I used product in a chilly 30 deg. F enviro with a cheap 40 deg. F bag. We had a stiff breeze and I would have truly froze if not for the use of this product. By fully enclosing myself in it and closing down exterior bag, I was able to resist wind penetration and survive the night in relative comfort and warm feet! I would have to say that claims of adding another 10-15 deg. F seem very true.

It is a simple addition when questions arise to a bag being a low enough cold rating on a trip. Weighs around a pound or so- but better than carrying a bigger bag instead.

I only have one bag that's rated at 40-45 degrees. Going on a mountaineering trip I needed a warmer bag, but money was tight. Camping on 3ft plus of snow at 5,000 ft in early May on the way to Mt. Stuart was very cold. Other people had between 20 degree and 0 degree bags. This liner helped me a lot. With my bag it performed almost as well as the 20 degree bag. It's very light and thin but does add around 25 degrees. It is very impressive. The value is pretty good too. I am gonna keep it in the car for travel and emergencies. It is nice to add range to your sleeping bag setup. It is hard to get the liner and bag to line up and fit well. Moving around can twist things up a bit. All in all it's pretty great.

I tend to buy a lot of gear- my wife says we have a mini REI in our basement. That being said, I sometimes buy gear that I use once, don't really like it and rarely use it again. I feared this liner would fall into this category, but I was wrong. It works great to add extra warmth to a sleeping bag, stands alone for a summer bag in warm places, and acts as a great liner when staying at a friend's cabing or home and don't want to have to wash all the sheets after the visit. It is a very soft, stretchy material that makes it feel larger than it is, making it very comfortable. It was pricey, but I am very pleased with the purchase.

I have used this bad as a liner and by itself on many occasions. In extreme cold it will lock in heat and compliment the best down bags when you have cold near zero temps. It will improve your bags rating about 10 to 20 degrees. This bag is not confining either. There is plenty of room for moving around in it as well. In warm summer months its just right to use by itself with temps above 60f or as a sleep sheet with a thin bag. It packs down to about the size of a soda can and takes up little space. I think its a good product and has kept me nice an warm when waking to ice condensation on the inside of the tent cold.

Im 5'2 so I had plenty of lenghth and room.. I would guess a 6' - 6'2 man would still find plenty of room, it does streach.. the fabric was soft and comfortable but, very sheer and light... I was very impressed w/ how increadably warm it was! I normally sleep in down mummy bag during fall camping trips but, I used my light weight mummy bag w/ extream thrmolight for a resent 3 day backpacking trip to cut down on volume and weight.. I was so warm that I slept w/ my bag open both night... this is amazing product for someone that has cold weather issues... I have Raynauds sysdrom in my hand and feet my body chills very quickly.... I WISH THEY MADE GLOVES :)

I bought this liner a few years back and have had a love affair with it ever since ... don't tell my wife. It packs super light and often times is the only thing I sleep in for summer camping. I most note that most of that camping is in Southern Utah, so it is a bit warmer than most areas. The material is soft and stretchy, so I never feel too restricted. It washes very easily, so it gives you peace of mind to know when you get a bit dirty and need a heavier bag, this liner will ensure you don't soil that bag. Thumbs up to you, Sea to Summit!