Sizing details/measurements:
Small: fits a foot length up to 9.0 inches/23cm: (women US size 5-6.5).
Medium: fits a foot length up to 10 inches/25.5cm: ( women US size 7-10/men US size 7-9.5). (Fitting note: if you area a size 9.5 and have a large volume/ wide foot, you should order the size Large for the best fit).
Large: fits a foot length up to 11 inches/28cm (women US size 10)/ men US size 10-11.5).
(Fitting note: if you are a size 11.5 and have a large volume/ wide foot, you should order the size X-Large for the best fit).
X-Large: fits a foot length up to 12 inches/34.5cm (men US size 12-15).