This purchase is for a pair of rear axle sliders designed to minimize damage to the front forks in a low-side. 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 bolts are made of highest grade commercially available 12.9(177,000 psi in tensile strength). The long bar is made of billet aluminum. Rest assured that you are getting the best material commercially available.