These systems are designed to provide an engine speed and position signal to most EFI systems, with control being enabled by the ECU (not included). The kit’s 3/8”, 11, or 12 magnet wheel will provide an accurate crankshaft speed and position signal to the ECU in the most-demanding of racing applications. These kits were designed specifically for use on early model Small Block Chevy applications equipped with a standard, aftermarket ATI Super Damper or Fluidampr “style” harmonic balancer. The 7” trigger wheel included with these kits was designed to center off of the hub of the balancer and therefore, does not require a centering ring for wheel centering. Consequently, these kits will not work on balancers which do not have a center-hub extrusion (i.e.: Innovators West, etc.). In addition, these wheels will only work with balancers having a 3-hole, wheel mounting bolt-pattern. On some vehicles the Crank Trigger Kit May require slight modifications to accommodate special engine plates, pulley system, etc.