The E14 fitting is also called thin fitting. The diameter of 14 millimeters was developed by Thomas Edison. This is also where the type designation comes from, (E) Edison - 14mm is a logical type name E14. Of these E14 fittings are LED light sources but of course also luminaires in which the E14 LED light sources fit. Both fittings for both the LED light source and the lamp holder are referred to as E14 screw fitting.