Sea To Summit Reactor Extreme sleeping bag liner is an essential component in your sleep system. The Reactor Extreme liner with Thermolite Pro fabric utilizes innovative infra red-absorbing ceramic pigments to give your system the thermal boost needed in colder-weather adventures. The soft, wicking stretch-knit fabric provides unmatched comfort and freedom of movement while still allowing the Reactor Extreme liner to fit any sleeping bag. Additionally, the drawcord footbox offers plenty of ventilation and the versatility of walking around camp while still wearing your liner if needed. Sea To Summit Reactor Extreme sleeping bag liner