Hockey skates are optimized for physical acceleration, speed and manoeuvrability. This includes rapid starts, stops, turns, and changes in skating direction. In addition, they must be rigid and tough to protect the skater's feet from contact with other skaters, sticks, pucks, the boards, and the ice itself. Rigidity also improves the overall manoeuvrability of the skate. Blade length, thickness (width), and curvature (rocker/radius (front to back) and radius of hollow (across the blade width) are quite different from speed or figure skates. Hockey players usually adjust these parameters based on their skill level, position, and body type. The blade width of most skates are about thick.