Accessories:Rear Knuckle Arm-2pcsStainless Steel Cap Head Screw 2.5x14-4pcsOriginal Name / Part No:AXI232047Part location:Rear knuckle armDoes this product replace a specific part or function?yesProduct major function & usage:stabilize rear axle and bearingMajor advantages of upgrading to this product:1.Aluminium 6061 T6 is a light material anodized for longer durability, corrosion resistant and aesthetics. It has a high tensile strength for greater durability when doing extreme RC action2. Precise bearing position minimizes the gap so the rear wheel joints can rotate smoothly, making the wheel more stable.