Here is the description from the website that best describes the sleep sack: Wearable blanket for safe sleep Keeps them cozy and can’t be kicked off Designed for a seamless transition after HALO SleepSack swaddle Zipper opens from bottom for easy diaper changes fabric is soft and super cozy Hip healthy design; approved by the International Hip Dysplasia Institute Extra length (so you don’t have to size up as quickly!) Comfy neckline with zipper covers to prevent scratches Baby size 18-24 months and 26-36 lbs. Gently worn but still comfy!