Sea To Summit Thernolite Reactor Mummy Liner is a sleeping bag that will keep you company during the night whether you are in bivouac, camping or trekking. The Thermolite fabric has light hollow core fibers that offer excellent heat but at the same time remain breathable. With the mummy shape it is compatible with all sleeping bags: use it to prolong its life! Reactor adds up to 8 ° to your sleeping bag! Sea To Summit Thermolite Reactor Mummy Liner sleeping bag liner