In order to respond to the movement of your feet, the shin and instep are divided to ensure ease of movement. The fingertips of the kick are also divided to allow for a subtle amount of force adjustment. Rubber fingertips to prevent slipping Size: XXS (Calf circumference: 9.8 - 11.8 inches (25 - 30 cm), Length: 16.1 inches (41 cm); XS (Calf circumference: 10.2 - 13.0 inches (26 - 33 cm), Length 16.9 inches (43 cm), XL (Calf circumference: 1.0 - 15.7 inches (3 cm), Length 2 inches (5 inches (5 cm).