Patented ATI Super Damper standard harmonic balancers are the only crankshaft dampers designed exclusively for high performance engines. Inner and outer shells are available in aluminum or steel, and contain a steel inertia weight. The inertia weights have six (2-ring design) or eight (3-ring design) computer-machined grooves to retain the proper durometer O-rings (dyno tested for each application). Whether you race or just drive on the street, ATI harmonic balancers are the perfect choice.Features include:* Eliminates torsional crankshaft vibrations* Exceeds SFI 18.1 specs* Black zinc chromate finished* OEM equipment on a variety of crate engines* Tunable, rebuildable, and extremely efficient at all rpm* Laser-engraved 360 degree timing marks* Supercharger and power steering drive pulleys available for some applications