The Fleece Sleeping Bag Liner adds extra warmth and softness to your sleeping bag. Adds up to 5-10 degrees of additional warmth to your sleeping bag. The fleece sleeping bag liner zips up just like a standard sleeping bag. You can even zip two together for an extra-roomy bag or to squeeze an extra kid or two inside. Built-in straps clip closed and include a handle for easy carrying. 240-gram non-pill fleece.