The Big Bore kit yields excellent results with stock cylinder heads (not for Twin Cooled motors). Easy installation: no need to bore or split existing cases, just swap the cylinders (unless noted). Cylinders are constructed from premium aluminum castings with cast-in iron liners. Kits include cylinders, pistons, rings and gaskets (head, base and exhaust). Black or silver powder-coat finish. Made in the U.S.A.. NOTE: This project requires a skilled technician. It is the responsibility of the person assembling the parts to check all clearances and assembly specifications..