The 'Easy Access' ST10 buckle and strap closure system is on the upper part of the boot making it easier to put on. The closure system, of the Sidi ST boot can be adjusted to comfortably fit your calf. The Ankle Brace System has a reinforced fibreglass protection beam on outside of boot hinged just above the ankle allowing for excellent movement front to back whilst being firm from side to side. The Air Ventilation system on the lower beam is operated using an aerodynamic slider. The Sidi ST has a composite inner sole, Leather outer construction, removable arch support and a dual compound sole. The boot is double stitched in all high stress areas. All bolt on parts are replaceable.