Voltage frequency Unit and internal voltage regulator kit with harness. This is a frequency module, NOT a Volt Meter. Comes with: Controller, Plug harness, wires , special voltage regulator and instructions. This is for Denso hairpin design alternators ONLY that are needing a lower voltage option for Headway cells around 14.4 to 14.6v. This kit allows you to set between 13.9v to 15.5v.