Phillips 15-730 7-Way Plug with Spring
The male plug w/spring is used on every truck out there pulling a trailer in the big rig world. It controls all the lights and in most cases the trailer brakes as well. This plug is only used in the big rig world; the light duty trucks have a 7 way but it utilizes flat blades on the receptacles; not round. It has a spring on it to help hold the insulated bundle of wires straight out of the plug, and also as a set screw to hold the insulated bundle of wires keeping them from getting pulled out. The internals of the plug uses set screws to wire up each colored wire correctly. This plug is used on the truck side of the wiring to be plugged into the receptacle on the trailer side transferring power from the truck to the trailer.