Dyna products has developed two "hot" coils for Big Twin and Sportster. These American made, top quality, High-Performance coils replace the stock coil. Dyna-mite coils produce spark Voltages in excess of 30,000 Volts and spark energies second-to-none. All Dyna coils are guaranteed against defects in materials and workmanship. Choose from three variations of resistance for different applications. Dyna coils are tested and proven on street, racing and touring motorcycles for over eight years. You can't buy a better, more powerful coil for your bike. Dyna-Mite coils are for use with stock and aftermarket Dual Fire ignition systems.