Glixal ATMT1-011 139QMB 139QMA Scooter Big Bore Cylinder Kit Rebuild Kit GY6 100cc 50mm Moped ATV Go-Kart 1.Please note this kit is only used for GY6 139QMB 4-Stroke Engine. 2.Inner Diameter of Cylinder: 50mm 3.Outer Diameter of Piston Pin: 13mm 4.Include Cylinder,Piston,Piston Ring,Piston Pin,Piston Pin Clip,Valve Oil Seal,Gaskets,Tensioner Gasket,Exhaust Gasket,Intake&Exhaust Studs,Exhaust Nut 5. High Performance Upgrade 50mm Cylinder Rebuild Kit for GY6 49cc 50cc 60cc 80cc 100cc engine