Customers often ask, Do I really need a harness? Yes! A relay harness is designed to deliver steady voltage to your HID ballasts directly from the car battery. Nobody likes a flickering headlight, so why risk it? Factory headlight outputs are really only designed to power a halogen light bub, not an HID ballast. As an important part of a finished headlight upgrade, don't skimp out when it comes to your wiring. The long list of features on the Morimoto HD Relay harness is easily worth the small premium over the eBay $10 special. It's wonderfully simple yet sophisticated layout make it universal across applications. The harness is designed to be plug-n-play on most any car or SUV that originally came with H8, H9, or H11 based headlights.