The Thermolite Reactor Extreme increases sleeping bag performance by up to 15°C with its super insulating 110g/m² Thermolite fabric. Spacious design allows for a comfortable night’s sleep, even when the mercury plummets. Thermolite is a fibre with a hollow core that provides extraordinary warmth for its weight while remaining extremely breathable. The Thermolite Reactor Extreme adds warmth to a sleeping bag or, used alone, is ideal as a warm weather bag. With the stretchy knit fabric that moves with you and a draw cord hood, this liner is perfect for wrigglers and rollers or anyone who needs some extra warmth.