What Are the Different Types of Light Bulb Fittings, Caps and Bases?

The part of the oven lamp or light bulb that connects into the light fitting is generally known either as the cap or base. Caps provide the electrical contact to conduct electricity to the light bulb but it also helps to secure the light bulb into its fitting.


There are a vast variety of caps and bases that exist in order to help make sure that only the correct type of lamp is used in any given fitting. This section shows many of the most popular fittings.






Named after the pioneering inventor Thomas Edison, the Edison screw oven lamp or ES lamp fitting is used worldwide in a vast range of applications. The most popular ES or E27 fitting is 27mm diameter and is widely used in UK and Europe. This cap is the standard 27mm diameter screw cap for UK 240V light bulbs – not to be confused with E26, which is a 26mm size and is designed for the 120V US market.






The G9 Oven lamp is specifically used for 240V capsule light bulbs. The light bulb can be identified by measuring the distance between the center points of the pins. The distance of a G9 measures 9mm.


LED Capsule Bulbs are now also available as an energy-efficient alternative to light bulbs. The fitments on LED capsules are exactly the same as those on halogen capsules, so if you’re replacing your current light bulbs with LED light bulbs and your fitting accepts one of the standard types listed here, you should be able to install them without an issue.






Different light bulbs are designed for different needs, environments, and situations. If you need a bulb that will last a long time, save you money and deliver bright light, then an LED light bulb with a high lumen output is best for you. If you want a light bulb that is budget-friendly, stylish and great for decorative lighting, then a candle-shaped halogen bulb with a low colour temperature is what you need.






UNDERSTANDING LIGHT BULB CAP TYPES AND BASE FITTINGS


Choosing the correct cap type or base fitting is the most important step when it comes to finding the right light bulb. The cap type or base fitting both conducts electricity to the light bulb and secures it into the fixture. Buying a bulb with the wrong Oven lamp holder simply means your lamp will not fit into the fixture – so it’s incredibly important you get it right.


The first letter of the code tells you the base or cap type of the bulb - such as a Bayonet Cap or Edison Screw Base.


The numbers reveal the diameter of the base, or the distance between the pins. This is listed in millimeters.


Some codes will also have additional letters after the numbers. This shows the number of pins or contacts the base has – such as ‘s’ for single, or ‘d’ for double.


So for example, the most common Bayonet Cap base fitting is listed as a B22d fitting. The ‘B’ stands for Bayonet Collar, while the ‘22’ means the base is 22mm in diameter. The ‘d’ at the end of the code means the base has two pins.






Candlelight bulbs feature a design based off the flame of a candle. This attractive ‘flame’ shape naturally gives them a decorative, elegant and vintage look perfect for ornamental lighting in hotels, restaurants and bars. As such, candle bulbs are most commonly used as decorative light bulbs in chandeliers, wall lights and exposed fixtures. Candle light bulbs are generally fitted with an E27 Edison screw base, E14 Oven lamp holder or B22 bayonet cap.


The Edison screw base is another of the most commonly seen base fittings in the UK. As their name suggests, Edison screw bulbs simply screw into the socket of a light fixture.


The most frequently seen size of the Edison screw is the E27 – a fitting that measures 27mm in diameter across its base. Other sizes of Edison screw are available, such as the E17, E26 and E39, but the E27 is the most commonly used in the UK and Europe.


E27s are available in a wide range of wattages and are used for a variety of applications.


Capsule bulbs sometimes called capsule lamps, use a push-fit base. Rather than being screwed or twisted into the fitting, these capsules have two pins in the base that allows them to be pushed into a fixture.


These small capsules are named and categorised by the distance between their two connecting pins. The G4 is one of the most frequently used bases for capsule lamps, and has pins that are 4mm apart. The G9 Oven lamp holder is also used for capsule bulbs, and features pins measuring 9mm apart.