Nilight USCAR 7 Pin to 4 Pin Trailer Wiring Harness Simple, plug-and-play installation Commonly for hookup of Trucks with original USCAR socket Retains functionality of factory-installed 7-way with extra 4 pin for trailer light 4 Pin female trailer harness output connection for light strips or other 4 Pin Connector trailer taillights, brake lights, and turn signals Directly plug into the back of your factory 7-way USCAR connector so you can retain the 7-way and also pull a trailer that has a 4-pole flat. Note: Vehicle must already be equipped with USCAR(factory-installed tow package)