The innovative design (patent pending) allows the seams on the upper side of a down sleeping bag to be completely avoided. Each seam is a weak point. The necessary seams on the side/underside are fully bonded.The Convertible Roof protects the head area against rain and snow.Dual Zip - two half zips on both sides allow the user to take our both arms to read or cook.The shelterTX™ outer fabric with waterproof yet breathable membrane offers excellent protection in rain and snow.The Shield is a sleeping bag and bivouac bag in one, but is lighter and cheaper than the combination of the two.