Revolution Performance Bolt-On Big Bore Kit (1250cc. Dished) - Bore 3.563in. - 10.5:1 Compression - Silver 201-415W Revolution aerospace-grade all-aluminum cylinders with nickel-silicon-carbide electroplated bores which means NO SLEEVING; allows larger bore sizes and less friction for more horsepower, lower temps and a longer lifespan True bolt-on kit that delivers major power with no machine work required Also includes Wiseco forged pistons with rings (that are specifically designed for optimal compatibility with Revolution Performances cylinders), wrist pins, circlips and high-performance head and base gaskets Available in four finishes: natural silver, black, black with highlighted fins or granite (matches engines of Screamin Eagle models) Replacement head and base gasket sets available separately