The 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.