Introducing the SwaddleMe Sack, a perfect extension to the SwaddleMe family of safe sleep products. Transition to a SwaddleMe Sack once baby starts to grow out of swaddling, or use with babies who don't like to be swaddled. The SwaddleMe Sack keeps baby sleeping safely on their back, yet allows for more movement for growing bodies. The soft cotton and sleeveless design help keep baby from overheating. The two direction zipper makes it easy for night time diaper changes, and the zipper cover keeps baby's chin protected. SwaddleMe - The Only One from Day One! Medium: 16-26 lbs. 100% cotton.