S&S 4-3/8 Stroke Flywheel For Harley Twin Cam A S&S Cycle is known for proven performance, so when you acquire anyone of their units you know you'll get just that. That is no different with this Fly Wheel Assembly. Expect performance gains and longevity out of this Flywheel. Features: 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