Vast improvement over stock flywheels which shift out of true under heavy load Heat-treated 4140 material is 114% stronger than stock, eliminates thrust washer Larger 1.671" crankpin, increased cross-sectional area for increased crank-pin clamping force Harder material, no thrust washers required, where stock flywheels have thrust washers S&S flywheels have steel gripping the crankpin No welding required Integral mainshafts,consistent balance and precision machining, truer flywheels and less vibration, and eliminates two potential points of weakness Reduced mainshaft deflection at high rpm, less vibration, reduced piston and rod side thrusting, prevents oil pump damage, fully compatible with gear drive cams Capable of higher rpm which allows more available power Includes sprocket bearing race; ; Note: Strokes longer than stock will require S&S Cycle piston oiler set 424-030. 2007-up stock rod length is 7.659". Stock pistons in 2007 and later engines require rods with tapered wristpin ends.; ; Note: Flywheel assemblies supplied with sprocket shaft bearing race installed are compatible with stock roller style sprocket shaft bearings. Assemblies with no race require a Timken sprocket shaft bearing.