Our 72cc piston ring set for 50cc GY6 QMB139 engine big bore kits contains all five Rings This is the same ring set that is included in our 72cc High Performance Cylinder Kit for 50cc GY6 QMB139 Scooter Engines (Standard) Description Our 72cc piston ring set for 50cc GY6 QMB139 engine big bore kits contains all five Rings. This is the same ring set that is included in our 72cc High Performance Cylinder Kit for 50cc GY6 QMB139 Scooter Engines (Standard). Please note that these rings are for the high performance 72cc piston, and will not fit the stock 139QMB 50cc piston. If all your GY6 engine needs are the rings, then this great deal from Monster Scooter Parts will save you money.