Find Your Store
Home Page

Cart, contains 0 items

When autocomplete results are available use up and down arrows to review and enter to select. Touch device users, explore by touch or with swipe gestures.
Expert Help
Earn Rewards

Sea To Summit
Thermolite Reactor Extreme Sleeping Bag Liner

4.679245283018868 out of 5 stars
106 Reviews

Out of Stock

Don't worry though, we have a lot more Sleeping Bag Liners in stock than that.

Shop Similar Products

Staying warm means staying happy.

The Sea to Summit Thermolite Reactor Extreme Sleeping Bag Liner is a great way to get an extra season out of your sleeping bag or stay warm in unpredictable weather. Lightweight and highly breathable Thermolite fabric will add up to 25 degrees Fahrenheit to your bag’s temperature rating at a low cost of 399 grams added to your pack. The Reactor Extreme has a mummy shape to mesh with your sleeping bag and a draw cord hood that can be cinched up when it’s really cold.


Details

  • Sleeping bag liner adds up to 25 degrees to sleeping bags
  • Thermolite insulation is light, breathable, and packable
  • Included stuff sack
  • Item #STS0084
Material
Thermolite
Shape
mummy
Degrees Added
25F
Stuff Size
6.5 x 4.5in
Claimed Weight
14oz

Overall Rating

4.5 based on 106 ratings

Review Summary

1 Stars - 0 reviews
2 Stars - 2 reviews
3 Stars - 5 reviews
4 Stars - 18 reviews
5 Stars - 81 reviews

Fits True To Size

Screen reader users: the following list provides a visual scale to illustrate the product fit. Please refer to the heading above for the fit type in text.
Runs smallTrue to sizeRuns large

What do you think about this product?

View

Selecting an option will reload the available reviews on the page
5 out of 5 stars

January 21, 2024

This liner is extremely versatile

[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.

Patrick K.
Sea to Summit

Originally reviewed on Sea to Summit

5 out of 5 stars

December 29, 2023

So cozy!

[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!

Matthew R.
Sea to Summit

Originally reviewed on Sea to Summit

5 out of 5 stars

December 29, 2023

Soft and Warm

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

Kevin S.
Sea to Summit

Originally reviewed on Sea to Summit

5 out of 5 stars

December 28, 2023

Sweet liner!

[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.

Chloe C.
Sea to Summit

Originally reviewed on Sea to Summit

5 out of 5 stars

December 15, 2023

It really worked!

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.

Brandon
Sea to Summit

Originally reviewed on Sea to Summit

5 out of 5 stars

December 11, 2023

Placebo or not?

[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.

Wade S.
Sea to Summit

Originally reviewed on Sea to Summit

2 out of 5 stars

November 29, 2023

No way this adds more than 3-4 degrees

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.

Scott
Sea to Summit

Originally reviewed on Sea to Summit

3 out of 5 stars

October 16, 2023

It’s very thin

I was expecting the traditional fleece. It did add some warmth and it saved me from freezing in my 30 degree bag when the temperatures dropped to the 20s on a recent trip. But I was still cold. I don’t want to return it because it’s a hassle and it does work but I didn’t see much difference from my regular western mountaineering liner and this one.

Fabexplores
Sea to Summit

Originally reviewed on Sea to Summit

5 out of 5 stars

October 7, 2023

Warm. Soft. Comfortable. Great addition

[This review was collected as part of a promotion.] Warm. Soft. Comfortable. Great addition to shoulder season camping

Daniel R.
Sea to Summit

Originally reviewed on Sea to Summit

5 out of 5 stars

October 6, 2023

Reactor extreme liner

[This review was collected as part of a promotion.] Excellent liner. Was great on a warmer night where I used just the liner. So soft it's like sleeping in your bed. Love it.

Jeff H.
Sea to Summit

Originally reviewed on Sea to Summit