E27 Bulb holder stands for the Stranded Screw where the 27 is the diameter of the light bulb cap and “E” stands for the Edison. So, this E27 is the standard and most commonly used bulb in the electrical field. E27 is 100 Watt of the voltage bulb but they consume 13 Watt approximately. So, those holders who hold the E27 bulb are called the E27 holders