The award-winning Sleep Suit Sack converts from a Sleep Sack to a Sleep Suit with legs using the 4-way zippers. The 400 thread count cotton outer has a silky smooth feel, and is made from an easy-care woven cotton fabric, similar to the feel of a flat sheet on your own bed. The stretchy side and shoulder panels are made from jersey cotton and ergonomically designed to allow your little one to move freely and prevent getting tangled during sleep.