The nikavi steel ball racer set is made from high quality stainless steel material. It is durable and long-lasting. Highly durable: The nikavi Yamaha R15 ball racer set properly casted steel will withstand intense impacts yet maintain its perfect shape. No alteration needed for installation. High quality: Less wear,smoother operation and longer life.Made From steel for durability and resistance to deformity under heavy loads. Tapered roller bearings decrease maintenance.Drop-in replacement for oem ball-type bearings. Less wear and longer life. Our nikavi ball raser set is suitable for Yamaha R15 motorcycle.