Understanding the different types of light bulb fittings in Europe and North America

Written by: Jean-Charles Lacoste



Time to read 3 min

Understanding the different types of light bulb fittings is essential when choosing the right bulb for a specific fixture. Each type has its advantages and applications, and selecting the appropriate fitting ensures optimal performance, longevity, and safety. Whether it's for ambient lighting, accent lighting, or task lighting, the variety of bulb fittings available allows for customization to meet diverse lighting needs in homes, offices, and outdoor spaces.

Edison Screw (E27/E26):

The Edison Screw, denoted by E27 in Europe and E26 in North America, is one of the most widespread light bulb fittings. Named after the inventor Thomas Edison, these bulbs have a screw-in base. The number following the 'E' represents the diameter of the screw base in millimeters. E27 is the most common size for household lighting, while E26 is often used in the United States and Canada. These bulbs are versatile and compatible with a wide range of fixtures, making them a popular choice for general lighting purposes.

Bayonet Mount (B22d/B15d):

In regions like the UK, Australia, and parts of Asia, bayonet mount bulbs are prevalent. The base of these bulbs has a push-and-twist mechanism for secure attachment. B22d and B15d indicate the diameter of the base in millimeters. The bayonet mount is user-friendly, offering a quick and easy way to install and replace bulbs. This type is commonly found in ceiling fixtures, table lamps, and floor lamps.

Candelabra (E12):

The candelabra base, denoted by E12, is characterized by its smaller screw size. These bulbs are commonly used in chandeliers, wall sconces, and decorative light fixtures. The 'E' stands for Edison, and the '12' represents the diameter of the base in millimeters. Candelabra bulbs are popular for their aesthetic appeal and are often used to create a warm and inviting atmosphere in residential spaces.

Intermediate (E17):

Similar to the candelabra base but slightly larger, the intermediate base (E17) is used in various lighting fixtures. This type provides a middle ground between the smaller candelabra base and the standard Edison screw base. Intermediate base bulbs are suitable for applications where a slightly larger bulb is required but a full-size Edison screw base is impractical.


GU10 bulbs are known for their twist-lock bayonet base and are commonly used in track lighting and recessed fixtures. The 'GU' stands for "glass and u-shaped," and the '10' denotes the distance between the pins in millimeters. These bulbs are often used for directional lighting, making them ideal for accentuating specific areas or objects in a room.

Bi-pin (G4, G9, G13):

Bi-pin bulbs have two small pins protruding from the base, and they come in various sizes. G4 and G9 are commonly used in smaller fixtures, with G4 often used in desk lamps and G9 in chandeliers. G13, on the other hand, is used in fluorescent tube lights. Bi-pin bulbs offer a secure and straightforward installation process, and their compact size makes them suitable for a range of applications.

Screw Terminal (E40/E39):

Screw terminal bulbs, denoted by E40 or E39, have a larger screw base compared to standard Edison screw bulbs. These bulbs are commonly used in industrial and street lighting fixtures. The 'E' stands for Edison, and the '40' or '39' represents the diameter of the base in millimeters. Due to their size, these bulbs are suitable for applications where higher wattage and intensity are required.


MR16 bulbs have a bi-pin base and are often used in low-voltage lighting fixtures such as track lighting and landscape lighting. The 'MR' stands for "multifaceted reflector," indicating the reflective coating inside the bulb that directs and focuses the light. MR16 bulbs are known for their versatility and are commonly used for accent lighting in both residential and commercial settings.

PAR (Parabolic Aluminized Reflector):

PAR bulbs come in various sizes and have either a screw or bi-pin base. They are characterized by their parabolic shape, which helps direct and control the light beam. PAR bulbs are commonly used in outdoor floodlights and spotlights for their ability to produce a concentrated, directional light. The different sizes cater to various lighting needs, providing flexibility in both residential and commercial applications.

Tubular (T8, T12, T5):

Tubular bulbs are commonly associated with fluorescent lighting. The 'T' stands for "tube," and the number following it represents the diameter of the tube in eighths of an inch. T8, T12, and T5 are common sizes, with T8 and T12 used in standard fluorescent tube fixtures and T5 in smaller, more energy-efficient fixtures. Fluorescent lighting is known for its energy efficiency and longevity, making it a popular choice for various settings.