Reality Check: Customers often ask, Do I really need a harness? Yes! A relay harness is designed to deliver steady voltage to your light bar directly from the car battery. Nobody likes a flickering light bar, so why risk it? Factory wiring just isn't designed for powering a beefy LED light bar. Plug n Play: The layout of the harness makes it easy to install. With just a few simple connections, even your mom could set this thing up! Wire lengths are long enough to be used in everything from compact cars to SUVs and it's designed to be 100% plug and play (no cutting or splicing needed). Fail-Safe: The included Morimoto Weatherpack 40A relay is completely sealed against the elements using ribbed silicone upper and lower seals, and has an flywheel diode for back-EMF protection. The on/off trigger and output are sealed with the proper silicone grommets. Live somewhere with weather that regularly sucks? No problem. Compatible: The Morimoto light bar harness is compatible with most light bars and pods with a 9006 input. OEM Grade: Aside from being ahead of the game from a technical standpoint, the HD relay is also a work of art. With it's wiring protected by abrasion resistant Techflex mesh sleeving and an OEM-level relay cube, the HD relay will look factory fresh under the hood!