The GPX 100 has, as you might've guessed, a pretty burly 100 flex rating, along with a relatively narrow 98mm last provides a snug, fairly aggressive fit that makes railing corduroy, skipping through bumps, and zipping between trees exercises in high-speed fun, not teeth-chattering terror. The Race GP Cork Fit Primaloft heat-moldable liner hugs the contours of your foot for comfort and precision, and the Full Shock Eraser bootboard takes the sting out of jumps, hardpack, and bumps so your feet absorb less punishment. Made of PU, and the cuff and shell provide a firm and consistent flex in all temperatures, and Nordica gridded the shell with its Bootfitter's Best Friend system, which makes it easier for bootfitting experts to punch and grind the shell to your exact specs. While the performance of the boot is awesome, comfort and customization are what sets it apart from similar boots. It has canting and flex adjustments, so you can personalize the fit, and all the hardware attaches by screws instead of rivets, so full customization is much faster and easier. GP dual-articulating buckles make opening and closing the boot super simple, and the Intuitive Easy Entry instep panel is softer than the rest of the boot, so no tears need be shed while you're trying to get your chilly boots on in the morning. Nordica also integrated its Full Motion Pivot, which allows increased customization around the ankle, and topped the GPX off with replaceable Extra-Grip soles for easier hiking and smoother parking lot navigation.