Base Types

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Vivid Leds, Inc. explains light bulb bases and how to measure and identify light bulb sockets and LED lamp base types. This description includes images and dimensions as well as information on E26, E27, GU10, MR16, G24, G13 and more. Light bulb bases and sockets are normally defined by a letter-number-letter format, with the last letter optional. The first letter designates the shape of the base and the numbers represent either the width of the base or the distance between the pins. The second letter designates the number of pins or contacts on the lamp. The numbers are normally in millimeters. LED light bulb sockets and bases are manufactured to the same standards as halogen, incandescent and other traditional lights. The standard USA screw-in incandescent bulb has a base type of E26. E stands for Edison screw-in and the 26 means that the base is 26 millimeters. E27 is the European standard screw-in size. LED light bulbs and LED lamps use the same socket designations. Retrofit Solid State Lights (SSL) that use LEDs or OLEDs are normally designed to be compatible with existing sockets. Please see the chart below for examples of each base.