This is my absolutely favorite costume. I bought it for my newborn and it was way to big so it is practically new and only worn for an hour at most. It is very soft and incredibly warm for your little one. It has a zipper that goes all the way around to the backside which also has an extra piece of fabric to help keep the wind out. Your little one will look adorable and be warm this season for Halloween and beyond. The sizing is 59/40 which was listed as 0-12 month. I would say 12month would be the largest unless your infant is on the smaller end. This will likely fit a 6-9 month old perfectly and run big or a little snug if they are average size and are younger or older. I would love to have someone else enjoy this amazing piece.