This is a complete top end kit for 50cc Chinese scooters with the 139QMB engine. Commonly called an 80cc big bore kit it is actually 72cc with a piston that measures 47mm in diameter. The cylinder kit includes, cylinder, piston, rings, wrist pin and gaskets. The head has preinstalled valves in either 64mm or 69mm size and you can choose EGR or non EGR style. This kit requires no modifications entailing machining the engine.