Sea to Summit Reactor Extreme Mummy Liner

[This review was collected as part of a promotion.] This liner is extremely versatile since it is comfortable by itself and increases the warmth of my 30 degree sleeping bag. The material is soft and good next to skin. I use it both couch surfing and when climbing.

[This review was collected as part of a promotion.] Where has this been all my life? My Boy Scout camping trips, field exercises in the Marines, and countless backpacking trips would have been so much more comfortable! Adds a noticeable bit of warmth, but the best part is that it feels like I'm sleeping in my sheets at home, rather than inside of a nylon bag. Love it!

[This review was collected as part of a promotion.] Light weight, soft and warm. Should work great as an additional layer in my system.

[This review was collected as part of a promotion.] This liner is awesome. I adds warmth, and saves me weight as I don't pack my zero down bag. I just take my lighter sleeping bag and this liner! I've used it inside my bag on hut trips when the hut is freezing at night in the winter, and on its own in the summer! It has become an all season add on for me. I am 5'4 and 120 lbs and there is plenty of room in there for me.

I went to Central Idaho for a seven day, six night elk hunt. Temperatures were projected to drop into the teens and low 20s most nights. My Kelty sleeping bag is rated to 20 degrees, but as we all know, that is not the comfort rating. I purchased this liner hoping it would give me the warmth I needed each night. It worked great. There was not a single night when I felt cold. Instead, I was truly warm.

[This review was collected as part of a promotion.] This thing is great for an added layer of warmth. It is lightweight and feels like a sheet inside your bag or quilt. Not sure yet on how much it adds thermally, but is good to fill those gaps around you to improve the bag’s efficiency. Is it a placebo effect? With it being as thin as it is, it does make you feel warmer by having more fabric contacting your skin. It also helps keep the bag/quilt cleaner which is a huge benefit.

Tested in controlled environment, at home, in November, thermostat set to where I would normally sleep cool and uncomfortable using summer sleep system. Added the Reactor Extreme to my kit and went to bed. Woke up cool, but not terribly uncomfortable so it took a little bit of the edge off. After giving it a lot of thought I believe that the material simply can't trap enough heat with as thin as it is to do much more than a 2-4 degree bump. As such, I can't imagine a use case where I would actually choose to put this in my pack. I believe that sleeping socks and cheap synthetic long underwear would work much better.

I’m not sure it adds 10degrees to my bag as claimed. I guess I just need to test it out in some colder weather.