Our Ultimate Crib Sheet rests over the existing fitted sheet and snaps to the crib rails with elastic tabs. No need to remove the bumpers or lift the mattress! Made of a polycotton blend with waterproof vinyl backing, the center is filled with layers of super absorbent padding that holds up to four cups of liquid. This ingenious item is a quick change sheet, mattress pad, super absorbent pad and waterproof pad all in one! Fits standard cribs.