With a traditional mummy shape, and a quilt style closure, the Sierra Designs Zissou Plus Two Season Mummy Sleeping Bag is unique, providing more bed like comfort. It intuitively adapts to varying temperatures, for 2 season use. Traditional mummy shape. Unique integrated quilt: Dual zip and trapezoidal shaped quilt provides bed like comfort in warm weather. Side wall baffles prevent down migration, keeping you warm. Anti snag zippers. DriDown 700 fill duck down insulation stays dry 10 times longer than untreated down and dries 30% faster.