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's a warm cuddly blanket they can't kick off; ensuring baby sleeps soundly throughout the night. Used in hospitals nationwide, the Halo SleepSack wearable blanket is the #1 choice of hospitals, recommended by safety organizations and is approved as "Hip Healthy" by the International Hip Dysplasia Institute. A portion of every purchase goes to First Candle/SIDS Alliance and The Canadian Foundation for the Study of Infant Deaths. Use over regular sleepwear to take the place of loose blankets. 100% polyester micro-fleece. 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.