6-way round plug to 7-way RV Socket Harness Adapter. Plug-is die-cast metal with high impact interiors. Brass terminal pins for best conductivity, terminals accept up to #12 gauge wires. Car-end only 7-way blade style socket of durable nylon with spring loaded door to keep out dust and moisture. Two 1/4″ mounting holes on 6-way sockets, 2-7/8″ on center, mounts through 1-3/8″ hole.