Interior lamp socket. Screw terminals backed out. Mandrel is insulated from mechanism, threaded 4-36 for knob. Fits 1-13/16" diameter socket cup. Knob furnished. Electroiler, 2-circuit, 2 filament lamps (also known as 3-way bulbs): Low-medium-high-Off. Rated: 250W/250V. UL (Underwriter's Laboratories) listed.