I read the reviews that said this was a snug fit, but ignored them. Learn from my mistake and listen when I say this sucker is a tight fit! My 7yo son is a stringbean(4'6" and 57 lbs) so I figured a 'slim' fit would be fine for him. When he put it on, it just fit with the straps fully extended and the bottom of the jacket skimming his belly button. It fits his 4yo brother perfectly (he's 42 lbs), so we kept it for him.