These wiring harnesses are designed to put an extra connector socket in the bed of your pickup truck while still retaining power to the rear connector socket mounted on your bumper. This is done by plugging into the back of the existing original equipment (OEM) harness and routing through the body of the truck to a hole in the truck bed, providing a connector that is ready to accommodate your 5th wheel or gooseneck trailer. This extension harness is designed to work with connectors 。When you need a towing electrical solution that allows you to switch back and forth between your receiver hitch and specialized trailer hitch, this wiring harnesses gets you plugged in.