Compu-Fire claims that their selectable advance curve ignition modules are the most user friendly ignitions on the market. They feature a range of advance curves that meet the needs of engines from stock to wild. The large rotary switches allow advance curve and RPM limiter selection. Easy installation is made possible with a built-in LED static timing light. The modules feature extended temperature and low voltage operation with soft start circuitry for easy starting. The modules operate with Single Fire or Dual Fire coils with a primary resistance between 2.5 and 3 Ohm. The VOES is tuneable. Use with ZPN238038 Tach Adapter for Single Fire use in combination with an electronic tacho. Available in a version for stock to mildly tuned engines, as well as a version for engines with a seriously increased compression. The High Compression version is not recommended for kick start use. These Compu-Fire ignitions fit 1970-1999 Big Twin (except Twin Cam) and 1971-2003 Sportster.