Bipin | 2-Pin Base
Each of these lamps has a bipin base. This means that they have two pins sticking out from the bottom of the light bulb. Not really rocket science, here. However, not all bipin base light bulbs are created equally. There are low voltage (6, 12, and 24 volts) and line voltage (120 volts); xenon, halogen, fluorescent, light sources; big and small; and, finally, the pins can be different widths apart. For example, a G4 bipin base means the two pins are four millimeters (4mm) apart.