Product Description MSD 8737 Multi-Step Module Selector From the Manufacturer Popular Two Step Module Selector with a third rpm receptacle! This third rpm function is designed for drag racing applications and is activated when vehicle is doing its burn out so that tire temperatures are kept consistent. SPECIFICATIONS Gives Ability To Choose 3 Different Rpm Limits Must Be Used with An Msd Soft Touch Rev Control Or A Timing Controller with A High Speed Retard Module Allows user to switch between 3 RPMtiming modules Set different RPM limit for burnoutlaunchover rev Can be used wtiming controls for retard changes Must be used with MSD soft touch rev limiter No RPM or Retard Modules are supplied