Sleeveless design reduces the risk of overheating; Generous sack design allows room for kicking, but cannot be kicked off so baby stays warm all night * Foot openings for mobility when awake; Room to tuck in feet at night * Use over regular sleepwear to take the place of loose blankets * 100% polyester micro-fleece * Size large fits 22-28 pounds, size extra large fits 26-26 pounds