Cotton 100% cotton premium fabric with no added chemicals. Now with two-way zipper and zipper covers at top and bottom. The only 3-way adjustable swaddle that adjusts to your baby's sleep style. Swaddle arms in, hands-to-face, one or both arms out to ensure baby's best sleep and an easy and gentle transition to the SleepSack wearable blanket when it is time to stop swaddling. #1 Choice of hospitals. Used by hospitals nationwide as their swaddle of choice for safe sleep education. "Back is Best" embroidery reminds caregivers to place baby on his or her back. Generous sack design allows room for kicking, but cannot be kicked off so baby stays warm all night. Recognized as "Hip Healthy" by the International Hip Dysplasia Institute. Use over regular sleepwear to take the place of loose blankets. Discontinue swaddling when the baby shows signs of rolling over or breaking out of the swaddle wrap. The HALO Sleep Sack Swaddle replaces loose blankets in the crib that can cover your baby's face and interfere with breathing. In addition to helping your baby sleep safer, it helps him sleep better, too. Its adjustable swaddle wrap immobilizes your baby's arms to prevent the "Moro" or startle reflex. And, it is the only 3-way adjustable swaddle that adjusts to your baby's sleep style. Swaddle arms in, hands-to-face, one or both arms out to ensure baby's best sleep and an easy and gentle transition to the Sleep Sack wearable blanket when it is time to stop swaddling. Used in hospitals nationwide, the Halo Sleep Sack Swaddle is the #1 choice of hospitals and is recognized as "Hip Healthy" by the International Hip Dysplasia Institute. Its strong adjustable fasteners ensure a perfect fit and resist breakouts for more secure swaddling. Plus, its innovative zipper, unzips from the bottom allowing your baby to stay swaddled for easy diaper changes. HALO also proudly supports non-profit organizations like First Candle/SIDS Alliance. Use over regular sleepwear to take the place of loose blankets. Discontinue swaddling when the baby shows signs of rolling over or breaking out of the swaddle wrap. 100% cotton interlock. TOG: 1.5 Size small fits 13-18 lbs. Durable Product.