LOT OF 4 The Radio Shack 272-0356 (E-10 THREADED Mini Lamp Base) is a set of four black plastic lamp bases designed for indoor use. The base is compatible with E-10 bulb wattage and has a screw connector. It has a voltage output of 2.5V and is energy efficient with an Energy Star certification. The base is 1.5 x 0.75 inches in length and width, respectively, and 0.75 inches in height. It is a circle-shaped base that can hold one bulb.