Fluorescent tubes generally have a two-pin fitting at both ends of the tube and generally, length goes hand in hand with wattage – the longer the tube the higher the wattage.
T12 38mm (G13) Fluorescent Tubes
The largest size T12 (38mm) is no longer being manufactured, however, they did use the same G13 cap as the T8 fluorescent tube which means that you can replace the T12 tubes with the more efficient T8 of the same length. See T8 section below for suitable alternatives.
T8 26mm (G13) Fluorescent Tubes
Standard size T8 (26mm) tubes use the G13 fitting with 13mm between the two pins.
T5 15mm (G5) Fluorescent Tubes
The small T5 (16mm) tubes use the G5 fitting with 5mm between the two pins.
T4 12mm (G5) Fluorescent Tubes
The undercabinet T4 (12mm) tubes use the G5 fitting with 5mm between the two pins.
T2 7mm (W4.3) Fluorescent Tubes
The ultra-slim T2 (7mm) tubes use a fitting called a W4.3 with 4.3mm wide push-fit fitting.
Colour Temperature
Although most lamps emit white light, this can vary from a cosy warm white to a cold white according to the colour temperature of the lamp. The following chart shows the code numbers used for some of the most popular types:-
| Colour Temp | Colour Code | Designation | Application |
|---|---|---|---|
| 2700K | 827 | very warm white | Similar light to incandescent light bulbs, giving a warm cosy feel |
| 3000K | 830 | warm white | The colour of most halogen lamps. Appears slightly whiter than ordinary incandescent lamps |
| 3500K | 835 | white | The standard colour for many fluorescent and compact fluorescent tubes |
| 4000K | 840 | cool white | Gives a more clinical or high tech feel |
| 6000K | 860 | daylight | Fluorescent or compact fluorescent lamps simulating natural daylight. |
| 6500 | 865 | cool daylight | Extremely white light used in specialist daylight lamps |
Colour Temperature Codes (for illustration only, colours may not be exact)
you can read more about colour temperature here.
Colour Rendering Definition
The Colour Rendering Index is an industry-standard reference to a light bulb on how well it renders colours of objects it is illuminating. Codes range from 0 to 100, the higher the number the more vivid and lively things look under that light. The lower the CRi rating the more ghostly (faded, dead) objects appear.
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Thanks for clearing up a query that was giving me a headache. Was trying to find a 4ft tube with a 38mm diameter which is apparently the old style tube and hard to find as discontinued. You can now use the newer T8 tube which is 26mm diameter but with the same end fittings. Many thanks.
Why don’t they put the color of the light on the tube. ? So I know what color to buy again.
Sometimes the colour is written in different ways. Look out for 3000K, 4000K, 6000K or 6500K which denotes the colour temperature in Kelvins. These can sometimes be written as 830, 840, 860 or 865 – where the 8 denotes that a triphosphor coating is used with a colour rendering index of 80+ and the next two digits are the first two digits of the colour temperature. Lastly, what is the colour of the light to look at; is it yellowish (3000K/830), white (4000K/840) or bluish (6500K/865).