The original wearable blanket replaces loose blankets in the crib for a safer environment; the #1 choice of hospital nurseries to promote safe sleep;Made from 100% cotton interlock fabric with a TOG rating of 0.5, offers just the right comfort for warmer seasons or climates; can be layered with warmer sleepwear for cooler temperatures; double knit construction of cotton interlock fabric makes it extremely soft & a little stretchy, perfect for baby sleepwear;Unique, roomy sack design recognized by the International Hip Dysplasia Institute as /''hip healthy/'' - allows room for kicking but cannot be kicked off, so Baby stays warm & safe all night;Inverted zipper opens from the bottom for easy diaper changes; sleeveless to reduce the risk of overheating; arm & neck openings sized for a safer fit;here in Medium size designed for babies weighing between 16 & 24 pounds who are generally 6-12 months old & 26-30 inches long