This purchase is for a pair of front axle sliders. 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 replacement nut and crossbar are made of 304-grade stainless steel for strength and rust-resistance. The nuts are made of grade 8, nylon lock type so they won't back out under normal engine vibration. Rest assured that you are getting the best material commercially available.