Types of lamp caps: standard marking and varieties of lamp caps

Vasily Borutsky
Checked by a specialist: Vasily Borutsky
Author: Mikhail Yashin
Last update: March 2019

There are various types of lamp base caps. The lack of a single standard is due to the size and power of the lighting device, the environment in which it operates, the presence of physical impact, and many other factors. All types and cartridges and socles are well-established marking, in accordance with which you need to make a purchase.

The purpose of the lamp base

The lamp base has two purposes:

  • Ensuring the operation of the device. The base and the cartridge have contacts as a result of the connection of which the light source is powered from the mains.
  • The ability to change the lamp in case of failure or the need to replace the device with other parameters. The base / cartridge connection should ensure the safety and ease of carrying out this operation.

Some types of lighting devices do not have a base. They are connected to the electrical circuit using flexible wiring.

Typically, this option is used for low power lamps, which are subject to physical shock or shaking. The connection “cartridge - base" in this case will be a weak point, as a result of which contact breakage will occur.

5W baseless lamp
The W5W baseless lamp is designed for 12 V. It is produced for a car lighting system, where the device operates in conditions of shaking and increased vibration

Types of connectors for lighting devices

Many countries have long implemented standards for lighting products. Now, in the period of globalization, you can buy devices from different manufacturers, including foreign ones. Therefore, the number of types of compounds is very large.

Type “E” - Edison Base

The oldest type of connection of a light source to an electric network is a standard and familiar lamp base in the form of a screw connection. The number in the marking, indicated immediately after the letter “E”, indicates the diameter of the thread in millimeters.In total, there are 10 sizes of the Edison base.

Lamps with the “E5” micro socle are often installed in foreign household appliances, appliances, and control panels.

Lamp with socket E5
Twelve-volt LED lamp of a direct current of the "E5" format. With the same micro-socle, devices rated for 6, 14 and 28 V can be purchased

The miniature base “E10” is used when lighting refrigerators, ovens and similar equipment.

Lamp with socket E10
Christmas tree lights are equipped with an “E10” connection. Under this format, most often you can find LED or neon light sources

Mini-basement "E11" is often used in foreign equipment. For domestic devices use light sources with a different connection.

Lamp with socket E11
This twelve-volt incandescent lamp operates on a direct current with a voltage of 24 V. It is used in medical technology

The “E12” format is used in the interior lighting of household appliances and in imported chandeliers.

Lamp with socket E12
These bulbs work from a standard 220 V network. They are rarely seen on sale, so their price is quite high

The “E14” format is often called the “minion”. This is one of the standard socles in the territory of the former USSR.

Many chandeliers, floor lamps, sconces are equipped with lamps with cartridges for 14 mm thread.

Lamp with socket E14
Under the “E14” base, you can buy ordinary cheap incandescent lamps, as well as expensive energy-saving LED products manufactured by well-known companies

Lighting devices in the USA and Canada have three screw connection formats. One of them is “E17”.

Lamp with socket E17
These lamps of original design are made in the USA and are designed for 110-120 V. For our networks, without preliminary voltage modification, they will not work

The second American format is “E26”. It is even more common than the previous one.

Lamp with socket E26
This LED bulb operates on a voltage of 110-120 V. For the “E26” format, there are cheaper, but less economical analogues based on a filament

“E27” - The most popular format in Russia. You can find light sources under this base in almost any store. Due to its prevalence, it is under this standard that most lamps are produced.

Lamp with socket E27
The most ordinary and familiar to all incandescent bulbs under the base “E27” are designed for 40, 60, 75 or 100 watts

Another North American “E39” format is designed for powerful light sources.

Lamp with socket E39
In fact, “E39” format lamps can be screwed into the base of the more common “E40” size. But we must remember that they work from a voltage of 110-120 V

The last in this list format “E40” is standard for Russia. Under it, powerful lighting devices are made, placed, for example, on lampposts.

Lamp with socket E40
Usually, under the “E40” format, they produce powerful incandescent lamps, as well as diode and gas discharge lamps, which consume from 100 to 1000 W

Now the proportion of lamps with Edison's base is declining. This is due to the use of more miniature and economical light sources. However, in Russia, the use of a threaded connection is still the most popular.

Type “B” - bayonet base

Bayonet (bayonet, pin) connection occurs due to insertion and rotation. It is used in many industries, including electrical engineering. The main field of application is lighting devices that operate under vibration conditions.

This mainly applies to transport. A bayonet connector is standard for electrical systems in the UK and some other countries.

Bayonet connection type
The bayonet type of connection is gradually replacing the classic threaded. It is easier to manufacture and use.

Mounts with this format are marked with the letter “B”, followed by a number indicating the diameter of the case in millimeters.

Depending on the number of contacts at the end, add another letter:

  • “S” (single) - one contact;
  • “D” (double) - two contacts;
  • “T” (three) - three contacts;
  • “Q” (quarto) - four contacts;
  • “P” (penta) - five contacts.

The format of a lamp with three or more contacts is assigned to a specific industrial equipment. They are not used in everyday life.

Lamp with socket B9S
A light source with a bayonet cap and one contact looks like this. 120 mA “B9s” incandescent lamps cost about 30 rubles

The car version is marked with the letters “BA”. The main difference is the length of the pin. In an ordinary socle, this parameter lies in the range [0.9; 1.1] mm, while in a car the minimum length starts at 0.64 mm.

Lamp with socket B15d
Base BA15d has two bare contacts. A threaded connection is not suitable here (as for all multi-contact joints), since the bulges may not coincide with the cartridge plates. Therefore, they use a bayonet system

In addition to the variety associated with the number of contacts, there is another feature that complicates the search for the desired type of bayonet cap lamp lighting.

In a standard connection, both pins are located at the same level horizontally and the angle between them is 180 °. But if after “B” or “BA” there is still the letter “U”, “X”, “Y” or “Z”, then this means that the pins are offset relative to their standard position.

Types of bayonet caps
GOST IEC 60061-1-2014 is an interstate standard establishing, among other things, the parameters of socles. The diagram shows a list of “bayonet” formats

Therefore, when buying bayonet lamps (especially for cars), you need to be very careful about each letter of the cipher that describes the base.

Type “G” - two pin connector

Another popular form of connecting the lamp to the network through a cartridge is a two-pin base. It is used in compounds of LED and fluorescent lamps. This mount is marked with the letter of the Latin alphabet “G”. The numbers that follow it indicate the distance in millimeters between the pins.

Like the bayonet connection, there are modifications to the “G” format. They are indicated by adding one of the letters “U”, “X”, “Y” or “Z” in front of the numbers. In this case, there will be some differences from the base format, which can be expressed in the thickness and length of the pins, the presence of grooves and cutouts on the base.

For example, the “GU4” format has thicker pins than the “G4”, while the type “GZ4” also has longer legs. Therefore, you must carefully consider the description of the connector, as modifications are not interchangeable.

Lamps with G4 socket
The “G4” pin bases are the smallest among this format. Usually they are equipped with halogen and LED lamps with a power of 3 to 20 W

Similarly look and use light sources with mounts such as “G5.3”, “GU5.3”, “G6.35”, “GU6.35” and “G8”.

Starting with the “G9.5” cap, the pins in the form of a wire are noticeably thickened.

Lamps with socket G9.5
Starting with the “G9.5” cap, the conductive contacts are much thicker and more massive. They are difficult to bend, which is often a problem when installing smaller lamps.

The “G9.5” format has three similar modifications with the letters “X”, “Y” and “Z”. In appearance they are almost the same.

Lamps with socket G * 9.5
The purpose of the lamp format “GX9.5”, “GY9.5” and “GZ9.5” is completely different. These are powerful luminaires up to 1 kW, powered by AC

Lighting devices with the connection format “GU10” and “GZ10” are produced mainly in China.

Lamps with GU10 socket and GZ10
The base pins “GU10” and “GZ10” have the original shape of the legs. This connection is equipped with energy-saving lamps made in China.

There is no “G11” format, but its paired version “2G11” exists. Also on 4 contacts are at the socles “2G7”, “2G23” and “2G27”

Lamps with socket 2G11
Some lighting fixtures require a 4-pin connection. In the photo - fluorescent lamps with high light output under the “2G11” base

The pins on the base “G12” and “G13” have the usual even shape. On the 13th format, tubular LED lamps work.

Lamps with socket G12
The cap format “G12” is quite widespread. Under it, both LED and ordinary lamps with a filament are produced.

The next two-pin connector is “G23”. It has an original appearance, very different from smaller devices.

Lamps with socket G23
Luminaires with a “G23” connector are produced mainly for special needs. On the photo - a bactericidal lamp made in Italy

The base “G24” is used for compact fluorescent lamps, the tube of which is folded four times.

Lamps with socket G24d- *
There are three modifications of the “G24” base, which differ in grooves. When using the wrong option, the lamp cannot be installed in the cartridge

Under the “G36” and “G38” connectors there are very rare lamps for use in narrow areas. So, the model of the halogen type Sylvania FKK CP73 / CP41 under the cap “G38” is used for photo optics.

Lamp with socket G53
LED and halogen lamps with a “G53” socket are powerful ceiling lighting fixtures. Instead of the usual pins, plates serve as a conductive element

The above list of two-pin connection formats shows what kind of different socles there are for bulbs of the same type. Therefore, if the marking of the cartridge is not known, then you need to carefully measure its parameters or come along with it to the store.

Type “F” - Single Pin Connector

Some types of tubular halogen and fluorescent lamps sometimes use single-pin socles, which are located at both ends of the lighting device. This solution allows you to simultaneously pass an electric current and securely fix the lamp. A mount of this type is marked with the letter “F”.

There are 3 modifications depending on the shape of the pin:

  • “A” is cylindrical;
  • “B” - grooved;
  • “C” is special.

The number that closes the code name of the cap means the diameter of the pin in millimeters.

Base type “Fa4” used for halogen lamps since the days of the USSR. Finding lighting fixtures and ammo for this format is easy.

Lamp with lamp base Fa4
The fastening of the “Fa4” format is provided by bright halogen linear type lamps with a power of 2 kW and a luminous flux of about 50 kLm. They are used in outdoor lighting systems, for shops and exhibition halls

The “Fa6” type connector is used by foreign manufacturers to equip fluorescent lamps. They are used where open fire is unacceptable by fire regulations.

It can be not only large, but also small-scale production. Wood or flour suspension can cause an explosion, so this source of lighting is relevant for the carpentry or flour mill.

Lamp with base Fa6
Specific fluorescent explosion-proof lamps, manufactured by the French company Philips. Using the “Fa6” connector avoids arcing on the electrical contact

For domestic purposes, you can also use lamps with the “Fc2” format.

Lamp with base Fc2
Metal halide lamp with a base “Fc2” can be used to illuminate large outdoor areas, such as the cottage’s house area

Sockets with knurled pins are now obsolete.

Type “R” - with recessed contact

This type is very similar to the “F” format, however the lamp contacts are recessed into the pin. The cartridge for such a base contains two spring-loaded metal protrusions that fix the lamp and provide electrical switching.

There are only two types of socles: “R7s” and “Rx7s”. The pin diameter for both options is 7 mm. The main difference in mounting geometry.

Lamp with socket R7s
Under the “R” type socles, both powerful halogen and metal halide, as well as ordinary LED and discharge lamps are produced

There is also a modification of “Rx7s-24”. The difference from the “Rx7s” is only in the length of the lamp - 132 mm versus 120 mm. Those. the base part is identical, and the “Rx72-24” cartridge length will be longer.

Type “S” - soffit base

The spotty type got its name because of the typical application of lamps - lighting of bathrooms and scenes, mirror lighting. It can be located on both sides for tubular lamps or in the form of a single base.

Designate this type of fastening by the letter “S”. The number following it shows the diameter of the base of the base.

Lamp with socket S6
Lamps with double-sided sockets “S6”, “S7” or “S8.5” are produced for the automotive industry. They are used to illuminate license plates and devices in the cabin

For tube lamps, the “S14” connector format is often used, for which there are two varieties. “S14s” models have two pins on the sides, and “S14d” have one pair in the middle. The shape of the base is different from the usual.

Lamp with socket S14
By their basic characteristics, these lamps do not differ from each other. Attaching to the cartridge also does not cause problems, so there is no reasonable advantage for one type over another

The cap shape “S19s” is a classic for spotlights.

Lamp with socket S19
Incandescent lamps with mounting type “S19s” are used in audio equipment, frequency translators and for other radio and electrical equipment. They can be purchased at stores specializing in the sale of electronics parts.

Lamps with a soffit base housing diameter exceeding 19 mm do not produce.

Type “K” - wired

Instead of the standard cartridge-base combination, a cable connection is sometimes used, which is called a wired base / plinth. It is marked with the letter “K”.

Wired lamp
The cost of high-pressure discharge lamps is at least 10 thousand rubles. They require high power (usually 1-2 kW) and emit light, brightness up to 250 kLm

Such lamps are used to illuminate large objects. Since the conditions for installing floodlights are different everywhere, the best option for connecting such devices is the use of a wired base.

Type “H” - for xenon lamps

The car has many different light sources. For accurate placement of light bulbs use special socles marked "H". This is primarily necessary for focusing the headlights. The number following the letter means a subtype of this format.

Car lamps of various types
Table of types of lamps used in cars. Now in all specialized stores there are electronic catalogs, according to which you can compare the nomenclature of light sources

The conductive plates are made in such a way as to fix the bulb in a certain position, taking into account the vibrations and shaking that occur when the car is moving.

Type “P” - flange plinths

The flange type of the base is used when it is necessary to clearly focus the light source, therefore it is often called the “focusing" one. Lamps with such a mount are used mainly in the automotive industry.

Flange Base Types
The diversity of car manufacturers has led to a significant number of formats, standards, and specifications. This was reflected in the light sources installed in the machines.

It should be noted that the shapes of the “P” type sockets are diverse and do not have any common geometric features.

Their separation into a separate type occurs only because of the property of clearly setting the light source relative to the reflector or lenses.

Type “T” - Phone Format

The telephone base is used for small bulbs that are installed in switchboards, control panels and cars. Light sources with this connection format are indicated by the letter “T” followed by a number indicating the diameter of the mount in millimeters.

Lamps with sockets T3 and T4.7
The smallest “T” mounts differ only in diameter. On the left is a lamp with a “T3” socket, in the center and on the right - with a “T4.7” socket

The “T6.5” format has a similar appearance. But the lamps with the “T5” base, which are used in the dashboard of the car, look different.

Lamps with socket T5
One of the most common types of telephone mounts is the “T5”. The base housing is made of plastic, so it is cheap

Two other formats that are often used for vehicles: “T10” and “T20”.

Lamps with socket T10 and T20
Sockets like “T10” and “T20” are identical and differ only in size. Such lamps are used to operate the dimensions, brake light, reverse signal, etc.

Since the LED bulbs are heated, the socles are made of heat-resistant plastic. It must withstand temperatures above 130 ° C.

Using base adapters

Sometimes situations arise when it is not possible to find a lamp with the required parameters for a specific format. For example, after buying a three-arm chandelier with “E14” lampholders, installing it and connecting lamps, it turns out that there is not enough light from it, even when using powerful LED sources, such as Lightstar T35, which produce 950 lm each.

In order not to change the chandelier, you can use special adapters from one size of the base “E” to another. Using the adapter “E14 -> E27”, it will be possible to connect lamps of the “E27” format, which can produce a more significant luminous flux. For example, the X-flash 50 model shines with a brightness of 1650 Lm.

Also on sale there are adapters from one type of cap to another. The most popular types are “E -> G” and vice versa. All these devices can be purchased in stores or ordered on well-known online sites.

Conclusions and useful video on the topic

Types of lamps for conventional screw cartridges:

It is necessary to buy a lamp in strict accordance with the marking of the cartridge. In simple cases, especially for the “E” format, you can do this yourself. But for other types, there are many modifications and nuances. In case of doubt, it is better to contact a specialist consultant.

If in the process of reading this article you have questions or have information supplementing the information presented, please write comments in the block below the text.

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Visitors Comments
  1. Vladimir

    Previously used lamps with E27 base, but with us they flew in chandeliers very often. Now switched to energy-saving.
    By the way, for the first time I heard that there are adapters for lamps.

  2. Unfortunately, sometimes there are situations when the standard marking of the socles begins to "slip". In particular, this applies to the Edison pinout, which in some countries is being remade in its own way. So in the States (and in some places in Canada), our standard E27 base is usually labeled as ES, and the smaller E14 as SES. These are abbreviations for the words Edison Screw and Small Edison Screw. There are the same for other E-shek.
    I also met Asian bulbs, the marking of which was not based on the type of cap, but on the outer diameter of the bulb, for example, T1 corresponds to 3 mm, T1½ - 4.5 mm, T2 - 6 mm, etc. Moreover, this is not a T base, but classic bulbs with a screw base.

  3. Stepan

    Standardization is our everything! At home - only E 27, all lamps, without exception, so as not to keep a different supply in case of failure.