BULB SCREW BASE TYPE E, The designation Exx refers to the diameter in millimeters, even in the U.S., where the bulb glass is listed in eighths of an inch. (For example, E5 has a diameter of 5 mm.) There are four common sizes of screw-in sockets used for line-voltage lamps: CANDELABRA: E12 North America, E11 in Europe / INTERMEDIATE: E17 North America, E14 (Small ES) in Europe. MEDIUM or STANDARD: E26 (MES) in North America, E27 (ES) in Europe. MOGUL: E39 North America, E40 (Goliath ES) in Europe.