Cotton 100% Cotton Use over regular sleepwear to take the place of loose blankets Ideal for the coldest of winter nights. TOG: 2.5 Size small fits 10-18 lbs; size medium fits 16-24 lbs; size large fits 22-28 lbs. Unzips from the bottom for easy diaper changes. Generous sack design allows room for kicking, but cannot be kicked off so baby stays warm all night. Sleeveless design reduces the risk of overheating Used by more than 1,250 hospital nurseries nationwide as their product of choice for teaching parents safe sleep practices. Recognized as "Hip Healthy" by the International Hip Dysplasia Institute "Back is Best" embroidery reminds caregivers to place baby on his or her back. HALO supports non-profit organizations like First Candle/SIDS Alliance.