These multi - function warm - up booties are designed for dancers. They can be worn both indoors (like in the studio) and outdoors (on the street). Sizing options are available as follows: XS (fits US 13.5 - 1.5), S (fits US 4 - 6), M (fits US 6 - 8), L (fits US 8 - 10), XL (fits US 10 - 12).