The patented ATI Super Damper is the only damper designed exclusively for high-RPM performance engines. The proven elastomer design is actually two dampers in one: a 4'' diameter and a 7'' diameter damper contained in two shells that bolt to the crank hub. The inner and outer shells are available in steel and in aluminum to contain the steel inertia weight. The inertia weight has eight computer machined grooves to retain the proper durometer O-rings (dyno tested for each application and installed at ATI). O-ring life has been tested to over two million cycles in Winston Cup competition and 10 years in drag racing engines. The unit is rebuildable to new specifications by installing new O-rings. Used on nearly all Winston Cup engines, the Super Damper's extensive dyno and on-track testing has proven it far superior to all other designs, especially on engines that turn over 6000 RPM. Shells are black zinc chromate finished with computer-controlled, laser-engraved 360° timing marks. Exceeds SFI 18.1 specs.