Swiftwick sizing is based on your corresponding shoe size. Please refer to the size chart below. CORE STYLES SIZE CHART MEN WOMEN EURO S 3-5½ 5-7½ 35-38 M 6-9½ 8-9½ 39-42 L 10-12 10-12 43-45 XL 12½-15 12½-15 46-48 Numbers above represent your corresponding shoe size.