Must use XL 1200 heads. 3.563" bore cylinders; 10.5:1 flat-top pistons Revolution Performance 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 Performance's cylinders), wrist pins, circlips and high-performance head and base gaskets; Note: For replacement pistons and rings, see Revolution Performance Big Bore Piston Kits.