The MummyLiner Coolmax from Cocoon adds warmth and comfort to your sleeping bag, while protecting it from dirt and body oils. A MummyLiner will extend the life of your bag by eliminating the need for frequent washings, which is how most bags are damaged. CoolMax is the fastest drying moisture management fabric. Its four channel fibers move sweat away from the body.Cocoon MummyLiners are specially designed to fit any tapered mummy sleeping bag. They feature a drawstring hood, a boxed foot end and are double stiched for durability. On a hot night, your MummyLiner might be all you need.