The THERMOLITE Reactor Fleece liner is Sea to Summit's warmest sleeping bag liner.

Add one to your sleeping bag before heading into really cold environments or, use as a 'stand alone' sleeping bag when the weather is warmer. The hollow core THERMOLITE fibers have the same hollow structure as polar bear – when made into a fleece, this traps a lot of insulating air.

Luxuriously soft, the Reactor Fleece is perfect as part of a cold weather sleep system – plus it will help keep your sleeping bag clean.