Rottefella Xcelerator Flexes are developed to adjust the way your skis respond. The flex is the "engine" in the binding, providing flex resistance and improved handling of your skis. They come in three grades of toughnesshard, medium and soft. All MOVE, Xcelerator and Performance bindings come with a medium hard flex. Lightweight skiers and skiers with small feet will benefit from a softer flex. The flexes do wear, so changing them once a year for maximum performance is recommended. Compatible ProductsMove Performance Xcelerator Pro Xcelerator 2.0 Xcelerator Junior Quicklock IFP Rollerski Sport Screw