Add warmth to your sleep system in cool or cold conditions: with Sea to Summit's Reactor Liner. Using Thermolite® Pro fabric with infrared-absorbing ceramic pigments and Thermolite® EcoMade fibres , the new Reactor takes thermal performance to the next level. The stretch-knit fabric provides optimal comfort, and ensures the Reactor fits any sleeping bag. The Mummy with Drawcord - the footbox opening offers plenty of ventilation and the versatility of walking around camp while still wearing your liner if needed.