The Montbell UL Spiral Down Hugger #3 has incorporated a classic tailor's technique to address sleeping bag comfort issues. By integrating a woven fabric "cut on the bias" and orienting the fabric's warp and weft threads at 45 degrees to major seam lines the sleeping bag becomes more fluid or elastic in nature. Additionally, "spring like" crimped fibers are used in the weave of the fabric to capitalize on their inherent stretch properties. The result is a flexible sleeping bag that makes "tent life" more bearable without the additional weight and fabric required in the plush Super Stretch™ System. Features: Spiral Stretch System (PAT.Pending) Box Construction: Eliminates cold spots resulting from sewn-through seams and allows down to loft completely. Neck Adjuster: a drawstring adjusts fit around neck Draft Tube: a single draft tube prevents air from circulating through the zipper Auto Locking Zipper: a locking mechanism has been integrated to limit zipper "slip" during the night. Tapered Stuff Sack: A tapered opening and "bias cut" fabric are utilized to facilitate easier packing. Cotton sack included Specs: Temperature Rating: 30 F / -1 C High quality 800 fill power down 12-denier Ballistic Airlight fiber nylon POLKATEX® DWR treatment Max User Height: Reg (5 ft 10 in), Long (6 ft 4 in) Inside Shoulder Girth: Reg (56.7"-68"), Long (61.4"-73.7") Inside Knee Girth: Reg (45.7"-54.9"), Long (49.2"-59.1") Stuffed Size: Reg (5.3" x 10"), Long (5.5" x 10.4") Weight: Reg (1 lb 3 oz), Long (1 lb 4 oz) Fill Weight: Reg (10 oz), Long (11 oz) Color: Balsam