Curt Manufacturing 57004 Towing Wiring Adapts a 7-way RV blade vehicle socket to fit 4-way or 5-way flat trailer plugs Enables vehicles with a 7-way RV blade socket to recognize LED trailer lights Built-in, integrated resistors for computers that don't recognize LED lights 4-way flat output connects tail lights, brake lights and turn signals 5-way flat adds connection for reverse lights