Which LED light bulbs to choose?

The right light source

Are you looking for practical lighting for your flat, home or office? Are you unsure about the choice of light bulbs and how they fit into your lamps? Take a look at the description of the most popular types of thread to find the perfect solution for you.


An E27 or E14 threaded bulb is a bulb that has a specific type of thread. They are named after the creator of this standard specification, Thomas Edison, and the ’27’ or ’14’ refers to the thread diameter in millimetres.

These threads are a type of screw connection that are widely used in lighting. They look like spirals running around the base of the bulb, and their function is to provide a safe and secure connection to the light fitting. These are standard thread types in many countries, especially in Europe.

These threads are widely used in various types of lighting, such as table lamps, floor lamps, ceiling lamps, wall lamps and spotlights. Please note that not all bulbs are compatible with every socket. Before purchasing a light bulb, it is always a good idea to check what type of thread is required by the fixture in question.


The GX5.3 thread is a specific type of light source that is popular with manufacturers of different types of lamps. This bulb is characterised by its narrow angle of light dispersion, intense light and low price.

GX5.3 bulbs are available in LED and halogen variants. The bulb with the GX5.3 thread shares many characteristics with other halogen fittings. The top part of the bulb is in the form of a hemisphere with a flattened top (or slightly convex top). As for the lower part, the actual GX5.3 thread, it consists of short, slender ‘legs’. The dimensions of the upper part of the GX5.3 bulb may vary, while the spacing between the “legs”, which defines the size of the GX5.3 thread, is 5.3 millimetres. The height of this bulb is approximately 48-50 millimetres and the diameter of the main part oscillates between 40 and 50 millimetres.

G13 thread

A bulb with a G13 thread is a specific type of light source, most commonly found among fluorescent lamps, popularly known as fluorescent tubes. With the G13 thread, we are not dealing with a classic screw thread such as E27 or E14. Instead, G13 is a connector type in which there are two metal pins at each end of the fluorescent lamp, which plug into the corresponding sockets in the lamp socket. The term ‘G13’ indicates the connector type (‘G’ – bi-pin) and ’13’ indicates the spacing between the pins, which is 13 millimetres


A GU10 or G9 threaded bulb is a type of bulb that has a specific type of connection. Unlike E27 or E14 type threads, the GU10 is not a screw thread, but a snap-lock system.

In a GU10 or G9 bulb, there are two metal pins on the base of the bulb, which are placed at equal distances from each other. These pins are used to plug the bulb into the bulb holder by rotating it. In this arrangement, ‘GU’ or ‘G’ indicates the type of connection and ’10’ or ‘9’ indicates the distance between the pins in millimetres.

GU10 and G9 threads are the typical connector used for halogen bulbs and some types of LED bulbs. They are mainly used in spotlighting applications such as ceiling spotlights, track lighting or accent lighting. These are places where strong, directed light is required.


The G4 bulb is a specific type of light source, similar to the G9 model, which is designed to operate on a reduced voltage of 12V. Although all G4 bulbs originally only operated on low voltage, models designed to operate at 230V are now available.

The G4 bulb is a small, low-power light source that can be useful as accent or supplemental lighting. These bulbs, available in traditional and LED versions, are typically used in furniture, desk and ceiling lamps. They are valued for their wide range of light diffusion, emitting white cool or warm light, and their versatility.

We can go from traditional lighting to a G4 LED bulb, which provides safe voltage and long-lasting performance.

The G4 thread is characterised by specific features, the most prominent of which are the straight, slender ‘legs’. Light bulbs with a G4 thread can take a variety of forms, the most popular of which are round (resembling a small plate), oval and cylindrical shapes. The lower part – the actual thread – is installed by pressing in.

The various shapes of G4 bulbs allow for their versatile use in both the furniture and construction industries. The varied forms of G4 LED bulbs make them an excellent alternative to traditional halogen lighting. The small size of G4 bulbs increases their range of potential use.

The foot spacing of the G4 bulb stem is 4 millimetres, while the rest of its dimensions can vary depending on the purpose, manufacturer and, of course, shape. Unlike typical incandescent bulbs, G4 bulbs are subtle and small, allowing them to fit into even the smallest lamps.

Different types of LED bulb shapes

A series

A-series bulbs have the classic shape that most people associate with an incandescent bulb. They are usually known as standard or GLS (General Lamp Service).

These bulbs are commonly available with both bayonet caps (e.g. B22) and threaded caps (e.g. E27) and have a wide range of applications. They are most commonly used in homes: in ceiling lamps, kitchen lamps, table lamps or floor lamps.

C series

C-series shaped bulbs (referring to Candle or to Conical) are all bulbs that mimic the shape of a candle flame. They are smaller than most other bulb series. Each bulb has a slightly different shape – the CA most closely resembles a candle flame with a slightly curved tip, followed by the C and B, which look more blunted and stylised.

These are commonly used in chandeliers, artificial candles, bedside lamps or decorative lighting such as Christmas lights. The values given with the shape type, e.g. C37, indicate the largest diameter given in millimetres.

R series

Reflector (R) or bulged (BR) bulbs are sometimes used interchangeably and may be internally lined with a reflective material that helps to emit light from the bulb for a wide beam angle. They may have a flat (R) or bulged (BR) surface made of coloured, frosted, clear or patterned glass or plastic to help diffuse and distribute light more evenly.

Typically, LED reflector bulbs are not covered with reflective material. This is because LEDs are highly directional and the entire light source can be directed outwards, rather than requiring a reflective surface from which to reflect.

The R (Reflector) and BR (Bulged Reflector) series of bulbs provide a very wide beam angle, making them ideal for use in a variety of both commercial and residential settings. They are most commonly used in track lighting, in lighting where recessed lighting is used or in display lighting. The value in the R50 designation indicates the diameter given in millimetres.

G series

The bulbs in the G series, referring to Globe, are spherical bulbs available in a variety of sizes. There are small golf ball-sized bulbs, suitable for small, enclosed fixtures, right up to very large spheres usually intended for display. Larger G-series bulbs are usually fitted with carbon or LED filaments, giving them an aesthetically pleasing appearance. The wide range of sizes makes them easily adaptable to different luminaires. The value in the designation e.g. G45 indicates the diameter given in millimetres.

T series

T-series tubular bulbs are available in a variety of sizes and shapes, from the familiar fluorescent lamps to the aesthetically pleasing tube-like shapes commonly associated with incandescent bulbs. The variety of sizes and stem types (such as E27, E12, G5 or G13) makes them suitable for a wide range of applications such as chandeliers, wall lamps, pendant lamps, warehouse lighting or garage lighting.

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