Diadora's ultra stiff X Vortex Pro Mountain Bike Shoes are designed to put maximum power to your pedals so can rip trails. Diadora uses a carbon fiber sole that registers a 1012 on the stiffness index to provide optimal power transfer. The X Vortex's upper features Suprell Tech Morpho AM Cage technology, which provides a snug and secure fit without restricting circulation. Diadora includes a removable abrasion resistant Duratech heel cup to prevent slippages, and a perforated EVA insert which is also removable that is breathable and adds arch support. Finally, The X Vortex lets you dial in the prefect fit with a two wire Boa closure system, which allows you to adjust the fit across the top of your fit and over your metatarsal area via two micro tune controls.