To allow you to use higher wattage bulbs in your headlights without frying your factory headlight wiring.

Plug and Play.

It uses your factory headlight bulb connector as the signal to turn on/off the relay kit.  Your factory headlight harness now only serves as a signal so very low amperage will go thru the factory wiring.

Also great to use this harness for rally lights or custom wiring of high power lights with 2 separate circuits.

Used, but still works.  Some dirty on the looms.

Comes with relay box with fuses inside.