Curt Manufacturing 57674 Towing Wiring Adapts a 4-way flat socket to fit 4-way flat and 7-way RV blade trailer plugs 4-way flat output connects tail lights, brake lights and turn signals 7-way connects tail, brake, reverse, turn signals, brakes and auxiliary power Integrated LED tester confirms proper vehicle and trailer electrical function Dust covers included to keep connectors clean when not in use