Thermarest Haven 20 Sleep System Temp Rating: -6 degrees C/20 degrees F 701 Fill-Power goose down box-baffled inside durable 20D nylon shell, combined with a full hood, foot box and wrap around coverage to provide reliable warmth Can be strapped to any mattress, used without straps in warmer weather of slip a tapered ProLite or ProLite Plus inside for maximum cold-weather perfromance. No more sleeping like a mummy, trying to find out which way is up, or searching for your zipper - we've delivered room where you want it without zippers or excessive air space for maximum efficiency Chest pocket keeps headlamps, hats, gloves, and music handy.