The Rottefella XPlore Backcountry Hard Flex provides increased resistance against the boot and a more controlled descent. We recommend Hard Flex if you plan to use the binding with Ice-Skates. Flex is a flexible pad which provides bending resistance. It helps you control the skis and gives you a more natural kick-and-return cycle. You can easily change the All-Round flex that comes with the binding to Rottefella XPlore Hard Flex for a better experience when skiing downhill. Comes in pairs.