SIDI Vertigo 2 BootSPECS Steel wire for calf adjustment and secure closure with replaceable upper and cable holder for longevity Fiberglass reinforced nylon braces offer front to back flexibility and lateral stability with built in air intake for enhanced comfort Small elastic panel ensures smooth zipper movement over the ankle for added convenience Polyurethane shell with a shock absorbing insert and 3 mm impact movement Rubber top sole provides grip and longevity for