The Sea to Summit Thermolite Reactor is made from the lightest weight Thermolite and is extremely breathable. Extraordinary warmth for its weight, this sleeping bag base layer adds up to 15 of warmth to any sleeping bag. Use alone for the ideal warm weather bag. Made from Thermolite, a hollow core fiber that provides extraordinary warmth for its weight, and remains extremely breathable. Lighter weight and more packable than fleece. Adds up to 15F8C to the warmth of your sleeping bag. Packs into its own sil nylon stuff sack. Mummy shape with a box foot. Draw cord hood with a mini cord lock. Dimensions: 84x 36 Pack Size: 3 in. x 5 in. Wt. 8.7 oz.