This purchase is for a pair quick release rear axle sliders. They provide indispensable protection for your beautiful expensive swing-arm. It also allows one to quickly remove the rear axle sliders without removing any bolts or screws like those in a typical rear axle sliders. It facilitates quick removal of the rear wheel. It is an essential convenience at the track where you can promptly raise your bike as soon as you pull in a paddock. The two sides of the axle sliders are attached by high strength Neodymium magnets. The slider pucks are made of UHMW-PE (ultra high molecular weight polyethylene), a tough plastic with good strength, wear resistance and dimensional stability. It is more dimensionally stable than Nylon and used in many industrial ball bearing and friction reducing applications. The inserts inside the sliders are made 6061-T6 aluminum for strength. Rest assured that you are getting the best material commercially available.