K2 Sports Men's Mach 100 Custom Fit X-Training 2012 Inline Skates (Black/Blue/Silver) K2 Softboot , the original, delivers unmatched comfort with the best fit on the market The Mach Hi-Lo is a revolutionary aluminum frame that utilizes an innovative 90mml100mm design to keep your weight over the balls of your feet and puts you in the proper skating position. Designed to feature all of the functional properties of K2's Stability Cuff with the addition of a stiff rear insert creating more support that is needed to get the most out of the bigger wheels in K2's X-Training series 100mm/90mm 83a wheels for a super fast smooth role to get you to the finish line faster. Integrating an intuition liner into a K2 Softboot enhances the comfort of the original Softboot as well as increases the performance by offering a true custom fit.