SIDI puts rider fit and performance foremost, and the results speak for themselves. Winning is SIDI's legacy, established by more than 50 years of footwear innovation in the pursuit of performance and helping athletes realize their fullest potential. SIDI - A continuing passion for craftsmanship. External ankle brace system. Nylon inner sole with removable arch support pad. Dual compound sole. Sidi's exclusive cam-lock buckle system for easy entry and boot removal while still offering a perfect glove-like fit. Bolt-on (no hook-and-loop!) replaceable, adjustable and aerodynamic nylon scuff pads on the toe. 1.7 mm thick Technomicro is used as a base material. ST Air version features a fully-perforated Technomicro material outer for maximum air flow. Double-stitched in all high stress areas. Closable air vents on the foot outer. All bolt on parts are replaceable.