Dual fire ignition system kit includes #A1666 Dyna 5 OHM ignition coil. The Dyna S ignition system is the same one used by top drag racers and road racers all over the world. The Dyna S is a completely self-contained electronic ignition system that utilizes your OEM mechanical advance unit. It is a Hall effect style ignition which uses magnetic pickups to trigger the spark. Fits Big Twin 1970/1999 & Sportster 1971/2003 (except EFI models, Twin Cam or Sportster 1200S)