This 4-3/8" stroke 8-1/2" diameter flywheel assembly replaces the original flywheels 2007-'16 HD big twin engines, when using stock pistons. Wrist pin end of connecting rods is tapered like stock rods. Sprocket shaft has the bearing race pressed on and is compatible with stock roller sprocket shaft bearing. Flywheel assembly is three piece design. Pinion and sprocket shafts are forged as part of the flywheel. The only joints in the assembly are where the 1.671" diameter connecting rod crankpin is pressed into the flywheels. Flywheels are CNC machined from heat-treated, closed die, steel forgings, which are 114% stronger than late style stock steel flywheels. Fully assembled with premium quaility S&S heavy duty 7.659" connecting rods, with tapered wrist pin ends, and dynamically balanced. Assembly is trued to less than .0005" runout on pinion and sprocket shaft bearing surfaces, making them capable of higher rpm and fully compatible with gear drive cams.