Juno Lighting T480WH Trac-Master Wishbones Low Voltage MR16 Lamp Holder, White Height: 5-3/8-Inch, Width: 2 -7/8-Inch Ceramic socket uses one 12-Volt, 20-75-Watt MR16 bi-pin lamp that is dimmable using dimmer specifically designed for use with electronic transformers Must be purchased with transformer T537 or T538 12-Volt solid state electronic transformer for installation on Juno track Constructed of molded polycarbonate yoke with die-formed steel ring Aiming capabilities are 90-Degree vertical aiming and greater than 360-Degree horizontal rotation which eliminates aiming dead spots