Wiseco (K103 61.5mm 2-Stroke Motorcycle Top End Piston Kit Fits: Kawasaki 500S, 500H1, 500KH, Mach III 1969-76 Dedicated forgings are used for superior strength to weight ratio utilizing aerospace alloy with a dome designed for improved flame travel and detailed skirt shape and profiles for stability and smooth operation in the cylinder bore Compared to cast pistons, forgings are tougher and more durable, and will stand up to the abuse that high performance motorsport applications require Each Wiseco piston is designed with the proper installed clearance to produce the most power, least wear, and best seal at running temperature, for each application 61.5mm bore