Top off your GM, Ford, or Chrysler Ignition system with these great new replacement coils. These Blaster coils have MSD performance in factory style housings! The windings and construction of these new ignition coils are similar in performance to the line of MSD Blaster-2 Coils. The coil has an increased turns ratio plus there is lower primary resistance than the stock coil. This all amounts to a bolt-in replacement coil that produces more output voltage. These coils will work with stock ignition systems as well as MSD equipped cars and trucks. If you plan to install an MSD Ignition with your Blaster TFI Coil, use a #121-8874 harness for a direct plug-in installation. For the Blaster GM Coil use #121-8876.