Convert 883cc Sportster models to 1200cc No need to balance since these pistons weigh the same as stock 883 pistons Cylinder head modification is also not needed The dished piston dome keeps compression down to a streetable 9.4:1 with stock 883cc heads Installing this kit takes the same time as replacing a stock top end Kit contains S&S Cycle 833-1200cc conversion pistons with rings and wristpins, S&S Cycle 3-1/2" bore cylinders, cylinder head, base and exhaust gaskets, assembly lube and instructions; Note: The cylinder fin profile does not perfectly match the fins on 2004 and later stock heads, but the difference is not considered to be objectionable.; Note: S&S Cycle does not recommend boring 2004 and later 883cc cylinders from 3" to 3-1/2" bore to increase engine displacement to 1200cc due to the large taper on the bottom of the cylinder spigot. New cylinders are recommended.