Magnetic footie, featuring our time-saving magnetic fasteners and no over-the-head design, gets baby dressed fast. *PRE, NB, and 0-3M sizes open from neck to upper thigh and have mitten cuffs.*6M-12M sizes open from neck to crotch with a roomy seat for easy diaper changes. *9-12M sizes and up follow tight-fitting standards and are meant to be snug and have grippy feet. Order one size up if your child is on the mid to high end of our size chart.