By helping to prevent blisters and improving in-between size fit, our Fin Boots are especially designed to be worn with fins. The boot has a soft, neoprene construction, flat-lock stitching, a durable, reinforced ankle and is color-coordinated by size. Male Sizes: S (5-7) Yellow M (7-9) Red L (9-11) Blue XL (11-13) Green For female equivalent, size down 1-2 sizes.