What are the types of light bulb fittings? Ultimate guide

There are several types of light bulb fittings: bayonet, Edison screw, knot, and candelabra. Bayonet and Edison screws are the most common, while knot and candelabra are less so.

Types of Light Bulb Fittings :

Each light bulb has a code that distinguishes its type of attachment. The letters generally represent the fitting’s name, while the numbers represent millimeters. An E27 is an Edison Screw bulb with a diameter of 27 mm, for example. Other designations include GU10, B22, and E14.

Different types of light fittings also have different maximum wattages. This is usually etched onto the fitting itself and corresponds to the size of the bulb. Higher wattage means a brighter light, but it also uses more energy.

ES (Edison screw) light bulbs

Types of light bulb fitting
E27 & E14

ES bulbs are some of the most popular lightbulbs on the market. The two main types of ES bulbs are E27 and E14 (also known as SES or small Edison screws).

E27 bulb

The E27 is one of the most popular bulbs used in lamps, and it is also known as an Edison big screw. E27 bulbs are available with incandescent, CFL, halogen, and LED fittings. The bulb has a 27mm screw cap that is installed into a lamp; it works with 230/240VAC.

E14 bulb

The E14 bulb, sometimes known as a tiny Edison screw, is a small-sized variant of an E14 light. Incandescent, CFL, halogen, and LED fittings are available for E14 bulbs. The 14mm screw cap on the bulb is what’s inserted into a lamp; it works with 230/240V electricity.

BC (bayonet cap) light bulbs

BC Light bulb

Bayonet cap bulbs require you to twist and lock them into the fitting. Bayonet caps are a kind of light fixture used in many parts of the house. One of the most prevalent types of connections is B22.

G4 and G9 light bulbs

G4 Bulb

G4 and G9s, or capsule bulbs, operate in a manner similar to bayonet caps; they need to be pushed in and then twisted and locked into place. The differences are that one uses two connection pins, which are approximately half the size of a standard thermocouple, and the other is made up of two connection pins, each less than 4 and 9mm wide resp. Most often seen in cookers hoods.

G4 Bulb

The GU5.3 is similar to the G4 in that it has two pins that are thin and little to connect to the light, however, it is primarily used for decorative and atmospheric lighting. These lights are most often utilized in floor lights, lamps, or pendant lights.

G4 bulbs are 12V connections that require transformers in order to function. The distance between the two pins is typically 4mm apart; they simply need to be placed into the available holes of the lamp and slightly clicked into place.

G9 Bulbs

G9 bulbs have two long pins that fit into a lamp. These bulbs are usually used in smaller lamps, such as wall or ceiling lights with small connection points. The distance between the two pins is 9mm; they slot into place without the need to do anything else.

GU5.3 and GU10 bulbs

Down and spotlights, as well as LED bulbs, are available in a variety of shapes and sizes. GU5.3 is one type of down, and GU10 is the other. Twin pins connect them together utilizing a push-and-twist mechanism.

GU5.3 Bulb

A GU5.3 or MR16 bulb has two thin and tiny pins that must be inserted into a lamp. Because it is compatible with 12V connections, it is the safest voltage for wet and exposed places, and as such is suitable for bathrooms, outside lights, and kitchen areas. The distance between the two pins is generally 5.3mm, and they are inserted into the lamp’s available holes and gently clicked into position. Please note that any 12V light source, regardless of its wattage, requires a transformer.


The GU10 fitting has two pins that connect to a lamp, typically for recessed or surface spotlights. The distance between the pins is 10 mm, and they fit snugly into available holes in the lamp. They are suitable for 230/240V power sources.

R7 light bulbs

R7s are light bulbs that are longer than others, with connections at each end. They typically emit more light and power than other kinds of bulbs, making them ideal for home security or flood lighting purposes.