Sierra Designs Backcountry Bed Duo 600 Sleeping Bag 600-fill DriDown insulation stays dry 10-times longer than untreated down and dries 30% faster. Zipperless design means no hardware, cords or Velcro to get in the way of your comfort. Catenary shaped opening is smaller than the bag width, so when you push out, the walls push in to seal out drafts. Versatile integrated comforter wraps naturally to your preferred sleeping position and allows for easy adjustment to varying temperatures. Insulated hand/arm pockets provide insulation under your arms when comforter is used outside the bag.