This big bore cylinder and piston kit contains S&S 4-1/8" bore cylinders and forged pistons, rings, wrist pins, head and base gaskets. Pistons are flat topped design intended for use with S&S Super Stock cylinder heads. The cylinders are machined with the stock bolt pattern and are intended for use in stock crankcases of 1999-'06 big twin engines. Designed for 4-5/8" stroke flywheels, resulting in 124" displacement. Cylinder finish is a durable wrinkle black powder coat. For best performance, appropriate camshafts, performance air cleaner, performance exhaust and fuel system tuning are required.