Size S: For small and/or narrow feet. This group includes children's sizes (under the guidance of an up-to-date specialist) or smaller sizes such as 34-35-36 with narrow feet and toes. They can also be used as a transition before moving up to size M (for very narrow feet and toes), but foot anatomy varies, so without seeing the foot, it is more difficult to give a fixed recommendation. 

Size M:  For normal and wide feet. One-size-fits-all (suitable for sizes 37 and up). For narrower feet/toes, make a more gradual adjustment to properly mobilize and prepare the muscles. 

.