"I purchased for my 11 week old assuming it would fit or be too big according to the weight and length, but it was so tight on him he cried when I was trying to put it on him, and he was well within the measurements, it only has snaps up the front and not in the crotch, so it is a little difficult with diapering for an infant, ended up sending it back and buying one at a halloween store and got size 12-18mos, the body fit and I rolled up the sleeves and pants. The hat was too big for him, but it was cute with my 3 yr old's Buzz costume."