Use over regular sleepwear to take the place of loose blankets. 100% polyester micro-fleece. TOG: 1.0. Size preemie fits birth-5 lbs; 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. #1 Choice of hospitals. Used by hospitals nationwide for safe sleep education. Back is Best" embroidery reminds caregivers to place baby on his or her back. The HALO SleepSack wearable blanket 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, the HALO SleepSack wearable blanket helps your baby sleep better, too. It is a warm cuddly blanket they cannot kick off; ensuring baby sleeps soundly throughout the night. Used in hospitals nationwide, the HALO SleepSack wearable blanket is the #1 choice of hospitals and is recognized as 'Hip Healthy' by the International Hip Dysplasia Institute. HALO also proudly supports non-profit organizations like First Candle/SIDS Alliance. Use over regular sleepwear to take the place of loose blankets. 100% polyester micro-fleece. TOG: 1.0. Size preemie fits birth-5 lbs; 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.