The MummyLiner Cotton from Coccon 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. Its high quality cotton is breathable, creates a natural vapor balance and is very comfortable against your skin.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.