1994-1997 Powerstroke 7.3L Fluidampr Harmonic Damper (720221)Using only three parts (a laser welded sealed housing, an internal inertia ring, and highly viscous silicone fluid between the two), SFI approved Fluidampr harmonic dampers can control all crankshaft vibration not just a limited frequency range. As a result, you get reduced wear on the main bearings and timing gear, more stable valvetrain operation, and less chance of crank failure.