The Mammoth Sleeping Bag Liner is constructed of a durable, brushed (polyester or cotton) fabric and the design minimizes twisting during the night. The top sides open 24? and fold down for easy entrance and exit. Safety Velcro tabs close the openings to keep out drafts. Square pillow hood and reinforced seams. Use liner with any Mammoth sleeping bag to improve warmth by about 10 degrees or by itself as a warm-weather bag or travel sheet. Machine washable and dryable. Includes stuff sack with drawstring, barrel-lock, and handle.