ST Racing a-arm set is constructed of CNC Machined from high grade aluminum material, these aluminum Rear A-arms will bullet proof your Traxxas Stampede and Rustler. For smooth suspension operation, the hinge-pin holes are fitted with machined delrin inserts. Each set of A-arms also comes with high-grade steel hinge-pin set w/e-clips. Solid in design and construction. (1 pair) Note: not compatible with Traxxas Slash as the Slash uses a shorter rear arm Go aluminum...because real trucks don't have plastic arms