Motor State Distributing has set the pace for highperformance automotive components for racing street and offroad use Features. 678 Harmonic Damper for LS1 SFI. Eliminates torsional crankshaft vibrations. Exceeds SFI 181 Certified 181 specs. Black zinc chromate finished. OEM equipment on ZZ572 GM Crate Engines. Tunable rebuildable and extremely efficient at ALL RPM. Laser engraved 360 timing marks. Underdrive Harmonic Balancer. SFI 181 Certified. Internal Balance. AluminumSteel Shell. BlackCompatibility. LS1 SFI