The Sierra Designs Frontcountry Bed SYN 2-Season is a zipperless sleeping bag with a unique design. Enter the bag via a large opening in the top ? the oversized, integrated comforter seals the opening so you sleep comfortably and naturally on your back, side or stomach. The oval opening is designed to intuitively adjust in width to prevent cold drafts, yet it won?t restrict your natural sleeping position.Versatile Integrated Comforter: Wraps naturally to your preferred sleeping position and allows you to easily adjust to varying temperatures. Self-Sealing Foot Vent: Zipperless vent self seals and can be operated from the inside using only your feet to easily adjust to varying temperatures. Insulated Hand/Arm Pockets: Provides insulation under your arms when comforter is used outside the bag. Zipperless Design: No additional hardware, cords or Velcro to get in the way. Catenary Shaped Opening: Opening is smaller than the bag width so when you push out, the walls push in, to seal out drafts. Adjustable Sleeping Pad Sleeve: Secures your sleeping pad to create the experience of a fully integrated bed. Fits mattresses 20-25 in. wide. Room for Standard Pillow: Hood is sized longer and taller to accommodate a standard pillow and your head. Fully insulated bottom.