Saves time because pistons already fit to the cylinders - ready to assemble out of the boxCylinders are constructed from premium aluminum castings with cast-in iron linersNo machiningNo re-balancing of 883 cc flywheelsNo cylinder head modificationsMust be used with 883 headsKit includes cylinders, pistons with 11.2 cc dish volume, rings and gaskets (head, base and exhaust)Made in the U.S.A.