Wiseco PK139 64.00 mm 2-Stroke ATV Piston Kit with Top-End Gasket Kit 2-stroke kits feature the Pro-Lite pistons that are CNC machined for optimal cam shape and profile for peak HP and service life Each piston is built from race proven designs that are chosen by the top race teams in all forms of racing including super cross, motocross, GNCC, superbike, and more Resistance to impact and fatigue