Sierra Designs Frontcountry Bed SYN 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.