eviton Brass Keyless 3-Terminal Less Set Screw Socket. Specifications include: 2-3/4″ Overall Height, 1-3/16″ diameter, Solid Brass Shell Socket, Edison (Standard) Base, 3-Terminal Sequence of Operation: Low-Medium-High-Off, Designed for 2-Circuit (3 – way) Lamp. Must be controlled by separate switch. Sequence of operation determined by method of wiring the circuit control switch. Terminal screws are color-coded nickel to screw shell, brass to center contact, black to ring contact.