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THERMOLITE Reactor Fleece Liner (Adds up to 32°F)

This liner is so warm you can use it in your sleeping bag or on its own


Size Guide

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The THERMOLITE® Reactor™ Fleece sleeping bag liner is a luxuriously soft and super warm liner that can bump up the warmth of your sleeping bag considerably. It can also be used as a stand-alone sleeping bag in warmer climates and has a quarter length zipper to control temperature and allows the user to get in and out of easily. The hollow core fibers that make up this fabric trap heat effectively, keeping you toasty warm.  If you're looking for a high warmth to weight ratio or a lightweight summer bag, this is an ideal choice.

Learn more about which liner is right for you HERE


Packed Size Comparison

A little larger than a wide mouth water bottle (BPA free of course)


14.8 oz ≈ Lighter than a roll of paper towels


Add a full season rating to your sleeping bag


Easy to wash and helps to keep your down bag cleaner for longer


  • Adds up to 32°F / 18°C of warmth to a sleeping bag
  • Technical mummy shape with one hand, easy to operate, drawstring hood
  • Quarter zip makes it easy to get in and out
  • Can be used as a stand-alone sleeping bag in warmer temperatures
  • Packs into its own Ultra-Sil™ stuff sack

Technical Features


The Reactor Series Sleeping bag liners, the Venture, Traverse and Basecamp synthetic Sleeping Bags and the foot boxes of the Women’s Altitude and Journey down Sleeping Bags use hollow core THERMOLITE® fiber to add warmth. These fibers trap extra air for insulation (just like the hollow-cores of polar bear or caribou fur).

In the liners, the knitted THERMOLITE® fabric is soft and stretchy and comes in three different weights: 80g/m² fabric used in the Reactor and the underside of the Compact Plus liners; a 110g/m² fabric which is used in the Extreme, and the core and foot box of the Compact Plus liner; and the Fleece, the warmest of all the fabrics.

THERMOLITE® is also used in the Air Sprung Cell sleeping mats.

Tech Specs

Product Details

Added Warmth
Up to 32ºF / 18ºC
Best Use
Camping, Winter Camping & Travel
Comes With
Ultra-Sil stuff sack
Thermolite fleece
Zip Options
1/4th length zipper
6 ft 6 in x 28 in / 200 x 70 cm
9 x 5 in / 22 x 13 cm
14.8 oz / 420 g
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