This is a 660cc Cylinder Kit With 9.1:1 Compression Ratio. Cylinder Has A 100mm x 84mm Bore & Stroke, Identical to OEM. Lightweight Aluminum Cylinder Body with High Strength Steel Sleeve. Piston Is Manufactured From High-Grade Cast Aluminum For Superior Life Expectancy. Base Gasket, Head Gasket, and O-Ring Included for Seamless Installation. Yamaha 5KM-11310-00-00, 3YF-11631-00-X0,2C6-11603-00-00, 3YF-11633-01-00. Cylinder Stud Washers (4).