These kits convert 1986-1987 XL1100 and 1988-2022 XL1200 Sportster to 1250cc displacement. No machining or rebalancing is required. Kit contains forged flat topped 3 9/16" bore pistons with coated piston skirts, S&S 3 9/16" bore cylinders, MLS head gaskets, base gaskets, exhaust gaskets, assembly lube, and instructions. Kits can also be used on XL883 when installed with XL1200 cylinder heads.