Sea to Summit Reactor series insulated sleeping bag liners can extend the comfort range and improve personal hygiene of any sleeping bag. Thermolite hollow core fibers are constructed like the fur of a polar bear, efficiently trapping heat and providing a luxuriously soft, comfortable feel. The knit construction also gives the liners a degree of stretch. Available in four different weights, Reactor technical liners effectively make your existing sleeping bag warmer and more versatile. The original Reactor is the lightest and most compact and can add up to 14F degrees of warmth. The Compact Plus is designed for women with a shorter length and includes heavier layers of Thermolite in the toe box and torso areas for extra comfort. The Reactor Extreme comes in two lengths and has heavier weight Thermolite throughout, extending the range of a sleeping bag up to 25F degrees. The Reactor Fleece is warm enough to use on its own, adding up to 32F degree while still packing down smaller than most fleece blankets. All Reactor liners are mummy shaped with a toe-box, feature a drawcord hood and include a stuff sack. Reactor Thermolite sleeping bag liners are lightweight, compact and easy to clean.