Xenon Kit | Single Beam Relay Wiring Harness with Resistors Hard wiring job or cutting of the wires is not needed! The relay wiring harness with load resistors is good for trucks and cars. This is a perfect choice for those who would like to make the lights last longer. HID Headlights | Universal Single Beam Relay Wiring Harness It is a wiring accessory for an existing system. HID Wiring Harness Designed to deliver steady voltage to your HID ballasts directly from the car battery. A relay wiring harness delivers steady voltage to HID kit directly from the car battery. It can be used for high beams, low beams and fog lights on most vehicles.