Sea to Summit Reactor Thermolite® Liner The “Reactor” is made from the lightest weight Thermolite®, that DuPont has yet approved. Thermolite® is a hollow core fiber that provides extraordinary warmth for its weight and remains extremely breathable. Adds up to 15 degrees of warmth to a sleeping bag or, used alone, is the ideal warm weather bag. Features: Lighter weight, more packable than fleece Adds up to 15 degrees of warmth to a sleeping bag Mummy shape with a box foot Draw cord hood with mini cord lock Color of liner is black Weighs just 9 oz Packs into its own 3” x 5” sil nylon stuff sack