Increases sleeping bag performance by up to 15°C with super-insulating 110g / m2 Thermolite® fabric. Spacious design allows for a more comfortable night's sleep, even when the mercury plummets. Thermolite® is a hollow core fibre that provides extraordinary warmth for its weight and remains extremely breathable. Adds warmth to a sleeping bag or, used alone, is the ideal warm weather bag. With the stretchy knit fabric that moves with you and a drawcord hood, the Thermolite® Reactor Extreme liner is perfect for wrigglers and rollers or anyone who needs some extra warmth.