This kit includes S&S 4-1/8" bore cylinders and forged pistons, rings, wrist pins, head and base gaskets and designed for 4-5/8" stroke flywheels, resulting in 124" displacement. Flat top pistons intended for use with S&S Super Stock cylinder heads Cylinders are machined with the stock bolt pattern and are intended for use in stock crankcases Wrinkle black powder coat finish For best performance, appropriate camshafts, performance air cleaner, performance exhaust and fuel system tuning are required (sold separately); Note: Crankcases must be bored to accept the larger 4-1/8" bore cylinders