Overview Light Socket Adapter: Medium Base to JC Bi-Pin Adapter. Quickly convert any medium based light socket to a JC Bi-Pin with ease. This allows you to use an MR16, MR11 any Bi-Pin bulb in a light fixture that originally has a medium based socket. Voltage 12V / 120V Converts Medium Base to JC Bi-Pin Adapts To GU4.0 to GU 6.4 JC Bi-Pin Socket