The E27 fitting is also called thick fitting. The diameter of 27 millimeters was developed by Thomas Edison. This is also where the type designation comes from, (E) Edison - 27mm is a logical type name E27. Of these E27 fittings are LED light sources but of course also luminaires in which the E27 LED light sources fit. Both fittings for both the LED light source and the lamp holder are referred to as E27 screw fitting.
