The THERMOLITE Reactor liner is Sea to Summit's top seller in the sleeping bag liner range. It's an excellent cold weather option for those who need additional warmth. The hollow core fibers trap heat and offer extraordinary insulating properties. This is a super stretchy, soft, and comfortable choice with a mummy shape, foot box and a drawcord hood. Compact and lighter weight than fleece, this is a best seller for good reason.
Packed Size Comparison: Similar to a small foam football
Weight: 8.7 oz ≈ Two sticks of butter
Warmth: Adds up to 14°F to the temperature range of your sleeping bag
Bonus: Easy to wash and helps to keep your down bag cleaner for longer