With a bright shell design, this bag alludes the feeling of warmth. Perfect for a winter backpacking trip, the Cosmic Down 0 retains warmth exceptionally well by utilizing an insulated draft tube with anti-snag design, an efficient, form-fitting hood, and full draft collar. Box-baffle construction, ground level seams, and differential cut maximizes the warmth of the bag and eliminates cold spots. The 58" dual slider zipper makes it easy to get into out of the bag. Once inside, adjustment of the hood is easy to do with the captured cord lock and Fatman and Ribbon(tm) draw cords, which have distinctive feel so you can determine which cord controls the top and bottom of the hood while dark. Finally, the internal liner loops can hold your liner in place while you sleep and the sleeping pad security loops will keep you on your pad (straps sold separately). Kelty has adopted the European Norm (EN) 13537 test process which provides a standardized comparison method for all sleeping bag brands so that it is easier for you to choose the right sleeping bag for your needs. The two temperature ratings listed are "Comfort" and "Lower Limit." Comfort is defined as the temperature that a standard woman (132lbs / 60kg) will be comfortable at versus lower limit which is the temperature that a standard man (176lbs / 80kg) will be comfortable at. For the Cosmic Down 0, the EN tested Lower Limit is 4F / -16C and the EN tested Comfort Limit is 17F / -8C. Everyone varies in how they sleep, so the temperature rating is only a guide and you may experience being warmer or colder depending on your set of circumstances.. Insulation: 550-Fill Power Down . Shell Material: 50D Polyester Taffeta. Liner Material: 50D Polyester Taffeta.