Sea To Summit Reactor Compact Plus Liner (adds up to 20°F) | Mummy | Red & BlackThe THERMOLITE Reactor Compact sleeping bag liner is the ideal choice for gram counters under six feet who want to add warmth to their sleep system. The worlds first hybrid sleeping bag liner uses a combination of two weights of THERMOLITE fabric, with the warmer fabric strategically positioned across the torso and in the footbox. The THERMOLITE fibers work like the hollow structure of a polar bear's fur, which traps extra insulating air. The Reactor