NCY 1100-1288 171cc Aluminum Big Bore Cylinder Kit for the Genuine 125 and 150 GY6 Scooters 61 mm Bore Size Turns you 150cc scooter into a 177cc No cutting required, with most 61mm cylinder kits, you have to cut the engine cases Light weight cut-down piston to increase performance 62.9mm Outer Cylinder Skirt Diameter