Weighted Table Base for Working Lamp - 1/2 inch (13mm) DiameterThis weighted round table base allows you to mount the working lamp (ML16221121) onto any flat work surface. Position the base anywhere on your desk to the desired lamp position. Hole diameter of 1 2 inch (13mm). Designed for swing arm working lamps with a 1 2 inch mounting post. Heavy duty die cast zinc base. Nylon bushing inside allows the lamp to swivel easily. White finish that is easily cleaned with a damp cloth. No Optical Data