This purchase is for a pair of no cut frame sliders for the models above. They provide indispensable protection for your engine case cover. 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. Replaceable pucks are available for purchase. The crossbar is made of 304-grade stainless steel for strength and rust-resistance. The aluminum spacers and inserts inside the sliders are made 6061-T6 aluminum for strength. Rest assured that you are getting the best material commercially available.