The size is 18-24 months from Baby GAP, but the fit is slim, so it's likely best for children around 18 months old. The foot portion can be fully covered or left uncovered, making it suitable for babies who are being held. The hat is the type that covers the head well, and I think it will keep them warm by protecting from the head to the neck. It was quickly outgrown, so it was only worn a few times and is in good condition.