Rottefella Xcelerator 2.0 Classic has a unique construction and low weight. This gives you more power and improved speed, and the low profile of the binding secures maximum control in the tracks. The NIS key included allows you to move the binding to the desired position; forwards for better grip or backwards for better glide. The binding is set with medium flex which easily can be replaced with harder or softer flex. The 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. Rottefella Xcelerator 2.0 Classic suits classic skis with NIS mounting plate.