Use over regular sleepwear to take the place of loose blankets; Size preemie fits birth - 5 pounds, size small fits 10 - 18 pounds, size medium fits 16 - 24 pounds, size large fits 22 - 28 pounds, size extra large fits 26 -36 pounds * Used by over 1,000 hospitals nationwide as their product of choice for teaching parents safe sleep practices; Recogized as "Hip Healthy" by the International Hip Dysplasia Institute