About the Product?100% Cotton?Use over regular sleepwear to take the place of loose blankets.?100% cotton interlock. TOG: 0.5. Size small fits 10-18 lbs; size medium fits 16-24 lbs; size large fits 22-28 lbs; size extra large fits 26-36 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.