Also available for the whole family! way more fun to put on than sweats, and cozier than regular ol’ pyjamas, our onesies are playful piece for keeping your little one toasty this season. -details- 0-6 m: body length:18.5" chest width: 9" 6-12 m: body length: 21.5" chest width: 10" 12-18 m: body length: 25" chest width: 11" 18-24m: body length: 28.5" chest width: 12" 55% cotton. 42% polyester. 3% spandex.