Identification Guide

Index Technology Colour Hazards
Fittings Identification Levels Timeline

At first glance the lighting market appears to contain an infinite variety of bulb shapes and sizes. In reality it is not that complicated and a little detective work will help identify just about any type of bulb.

Before we begin...

If you haven't read our types guide then we would suggest you have a quick flick through this first. We will be looking at the distinguishing features of these technologies to help identify the bulbs. The cap or fitting guide is a seperate topic as some technologies use the same caps as others and some are unique.


Incandescent Lighting

Incandecent bulbs work by passing an electric current through a wire until it glows hot. This wire must be protected from the oxygen in the air so is always surrounded by a glass bulb. The very first electric light bulbs used hand blown glass envelopes which could not be formed into complicated shapes. This evolved into the GLS or pear shaped bulb which was the standard bulb for around 100 years.

Clear GLS bulb   Opaque GLS bulb


It was not long before the glass envelope or bulb was altered in shape for different applications

Candle   Large Globe   Small Globe   Pygmy


Before fluorescent tubes were commercially available and because of their limitations manufacturers developed incandescent strip lights. Resteraunts also use these bulbs as the heat helps keep the food warm. There were two versions of these and both variations came in clear and opaque. The easy way to identify these is by their cap, more details in our fittings guide.

Atchitectural   Picture


Parabolic Aluminised Reflector or PAR bulbs are commonly found in domestic and commercial lighting and come in a range of sizes.

PAR 38   PAR 64


A Note about colour

Having an opaque white coating on an incandescent bulb diffuses the light a little giving a softer effect but it is not necessary for the function of the bulb. In contrast fluorescent tubes must have an opaque coating as it is this coating that produces the visible light. HID lights are usually clear.


A Note about PAR size

The numbers represent the maximum diameter, either in eighths of an inch, or in millimetres, depending on the shape and the region. For example, 63 mm reflectors are designated R63, but in the U.S. they are known as R20 (2.5 inches).



Halogen Bulbs

As discussed in our types guide the halogen bulb operates at a higher temperature and higher pressure than a conventional incandescent bulb. This means the bulb must be made of a thicker and higher grade glass than incandescent bulbs, to keep costs down the bulb is usually a small capsule fitted into a variety of housings.

The common spot type halogen bulbs are actually a small capsule surrounded by a larger reflector body. The GU10 and GZ10 are 240V bulbs with a 50mm diameter, the GU5.3 is a 12V bulb with a 50mm diameter and the GU4 is a 12V bulb with a 30mm diameter. The GU10 and GU5.3 both use a MR16 capsule and the GU4 uses a MR11 capsule. Just to confuse us the 12V versions are commonly known by this capsule name but the 240V versions are commonly known by their reflector name.

Reflector GU10   GZ10   GU5.3   GU4
Bulb MR16   MR16   MR16   MR11
Voltage 240V   240V   12V   12V
Face Diameter 50mm   50mm   50mm   30mm



The halogen capsules are available without a reflector housing. These are available in either single or double ended capsule. The double ended capsule is 240V and typically used in flood lights and the single capsules are available in both 240V and 12V fittings for a variety of uses.

Ends double   single   single   single
Capsule R7   G4   G6.35   G9
Voltage 240V   240V   varies   240V



Fluorescent Bulbs

Standard fluorescent bulbs are all long tubes of varying diameters and sizes. The four diameters in common use are T5 in newer installations, T8 and T12 in older installations and T4 is task lighting such as under cupboard.

    T4 14mm Diameter G5 Cap
    T5 16mm Diameter G5 Cap
    T8 25mm Diameter G13 Cap
    T12 38mm Diameter G13 Cap
T5 Tube   T8 Tube        



Compact Fluorescent Lamps (CFL)

Compact fluorescent lamps use different ways to package a long tube into a small area. Most are simple loops or spirals but there are no limitations to the designs that are available.

Integrated compact fluorescent technologies are designed to replace existing incandescent bulbs and may be designed to look like the bulbs they are replacing.

Type Bi-Turn   Tri_Turn   Spiral   2D
Ballast Integrated   Integrated   Integrated   both


Non-Integrated compact fluorescent technologies are used in new buildings where the government requires a certain proportion of lighting to be energy efficient. By removing the balast from within the bulb and changing the fitting it is more difficult for home owners to revert back to less energy efficient technologies.

Type Bi-Turn   Uni-Turn   Tri-Turn
Fitting GX24q-1   G211   GX32d-2


Although there are common CFL bulb types that are easily recognisable there are also many variations that may not be easily identifiable. In this instance record the cap and product code from the bulb or box.



High Intensity Discharge Bulb

High intensity discharge bulbs are either a bulb or capsule shaped. The bulbs tend to be used in low pressure applications and capsules tend to be higher pressure although this is not always the case. Our types guide has some more information about this technology.

Type LP Sodium   HP Sodium   Metal Halide   Metal Halide
Cap B22   E27   R7   G12
Shape Bulb   Bulb   Capsule   Capsule


HID bulbs tend to be used in specalist applications so if you need a more advanced guide then we suggest you have a look here.


Why So many variations?

As consumers we have two conflicting requirements for lighting, we are asking for brighter lights in a wider variety of shapes and colours with an ever increasing convenience but at a reduced cost both to buy and use. The wide range of shapes helps meet our desire for variety and the different technologies help reduce running costs and introduce new colour options. LED technologies will give us even more opportunity to reduce bills, help the environment and increase our options, please just ask us if you have any specific requirements?