If the planned repair involves the replacement of lamps, then, choosing among the variety of types and designs of lighting devices, you should not forget about which lamps will be used, how they will be connected to the selected light source. One of the most important parameters is the type of bulb base. Let’s consider what types of lamp bases exist and how to distinguish them from each other.

To explain the purpose of the plinth, an international alphanumeric marking is adopted, which defines the characteristics. Some types of lamp sockets are widely used in everyday life, the use of others is limited to use in production, in various equipment, and in transport.

types of lamp sockets
Bulbs with a base of type E

Threaded (E)

For more than a hundred years, the base, developed by Thomas Edison, who offered a convenient and reliable system for quickly attaching lamps, has been successfully used. It is marked with the letter “E” in his honor. Now there are several types of such a plinth, which differ in diameter, which reflects the numbers in the name. Let’s list them:

  • E5 (LES) is a rarely used micro socket with a diameter of 5 mm.
  • E10, E11, E12 (MES) – minicircles with a diameter of 10, 11 and 12 mm, respectively. They are most often used in flashlights, various garlands, etc.
  • E14 (SES) is a 14-mm small socket, called a “minion”.
  • E17 (IES) is an intermediate socket with a diameter of 17 mm, which is used mainly in America.
  • Е26, Е27 (ES) – became a classic socket with a size of 26 or 27 mm, and the first of them is practically not used in Europe. We use E27, with which a large number of various lamps (incandescent, energy-saving, LED) are produced.
  • E40 (GES) – used for powerful light sources, mainly in production for lighting large areas.

This design has one drawback, which may appear after long-term operation of the lamp. It happens that when trying to unscrew a failed light source, the glass bulb breaks off from the base, leaving it in the cartridge. It is not difficult to turn it out, but it is worth remembering this drawback, and not to make great efforts when trying to remove the lamp.

Contact (G)

Also popular is the cycle type, most often used by halogen, fluorescent and LED lamps. The connection is made using two or more pins, the distance between which is shown in the marking. The number of pins can also be specified: 1 (s), 2 (d), 3 (t), 4 (q) or 5 (p) pins.

There are modifications that are indicated by the corresponding letter:

  • “U” is for energy-saving lamps.
  • “X” is a source with directed light.
  • “Y”, “Z” – modifications for specialized light sources that are rarely used.

Although the modifications may be of the same size, they are not interchangeable.

base G9
LED lamp with a G9 base

Varieties by size:

  • G4, GU4, GY4 – a miniature, 4 mm socket, which is usually used to connect low-voltage (12/24 V) lamps. It is used as spot lighting, in built-in lighting systems and other auxiliary lighting.
  • G5 is a base with a pin spacing of 5 mm, used in T4 and T5 compact daylight lamps (12 and 16 mm in diameter, respectively).
  • 3, GU5.3, GX5.3 – a distance of 5.3 mm between contacts. The most common GU5.3. It can be powered both from a 220 V network and from a low-voltage source. It has wide application. Many LED lamps use this size.
  • G9 – often used in chandeliers to connect halogen and LED lamps to the 220 V network.
  • GU10, GZ10 – a distinctive feature – the presence of thickening at the ends of the lamp pins. Installation is carried out by turning and fixing the light source in the cartridge. Modifications differ in the presence (“GU”) and absence (“GZ”) of a chamfer around the leg of the lamp, due to which GU10 can be installed in both types of socket, and GZ10 – only in its own.
  • G12 is a 12-mm socket for connecting a metal halide lamp.
  • G13 is a common type used in T8 and T12 fluorescent and LED tube lamps (25 and 38 mm in diameter).
  • GX23, GX24 – a base with a distance of 23 or 24 mm and with a built-in starter. It can be found in table lamps and other various lamps.
  • G53, GU53, GX53 – distance of 53 mm between contacts. The most popular is GX53, which due to its small depth (only 28 mm) allows you to install spotlights in the suspended ceiling with a small distance to the draft ceiling.

Soffit (S)

The method of attaching lamps with this base is known to many by ceiling lights for interior lighting or car license plates. The contacts are located at the ends of the lamp, the diameter is indicated in the marking, for example S6, S8.5. They are more often used to illuminate common areas, mirrors, etc.

plinth B
LED lamp base BA9s 5730

Pin (B)

This type was developed in order to improve the Edison plinth. Another name is a bayonet. Two protruding pins are made on the housing, which go into the corresponding grooves of the cartridge, after which the light bulb is rotated and fixed. This type is often used where the lamp may be subject to vibrations. The marking indicates the diameter of the case, as well as the structural arrangement of the pins:

  • BA is a symmetrical arrangement.
  • BAZ – the pins are shifted along the radius and are at different heights.
  • BAY – pins at the same height, but offset in radius.

The last 2 types are used where precise positioning of the lamp is required to form the correct direction of the light beam.

plinth R7s
Lamp LED Uniel series J LED 12W, base R7s


With recessed contact (R)

A specific base that is used in floodlights and lamps with high power and high temperature. Used to connect tubular halogen, LED, quartz lamps. The marking (R7s) indicates the diameter (7 mm) with two contacts (s), and the additional numbers 78 or 118 indicate the length of the light source.

Focusing (P)

Another base for specialized use in lanterns, navigation lights, searchlights, in all devices that have special requirements for the shape and direction of the light beam. For this purpose, the plinth has a special lens that provides the specified characteristics of the light beam. The numbers indicate the diameter of the flange in which the lamp is installed.

plinth P
Incandescent lamp Philips Vision P21W 12V 12498CP

Telephone (T)

The field of application is illumination of devices in cars, indication on control panels, mnemonics, etc. The contacts are located on all sides of the lamp, to replace which it is necessary to simply pull it out of the cartridge. The inter-contact size is indicated in the marking. LED technology is increasingly being used.


Despite all the variety, the most familiar and often used are the E and G sockets, which can be found in almost any household lighting device. The remaining types are specific and have a limited distribution. When choosing a lamp, you should specify the type of base, the nomenclature of lamps, so that no problems arise during their subsequent replacement.

Types of lamp sockets for home lighting

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