Osram Dulux Stick 20W 865 E27

The cap/base of a bulb is the part that connects it to the socket in the fixture. In the UK, B22 (Bayonet) caps/bases are still the most popular, although E27 (Edison screw) caps/bases are becoming increasingly popular. GU10 is the most common cap/base for spotlights. Check which cap/base you need carefully as many other types are also available.

The colour temperature refers to the colour produced by a light. It's measured in Kelvin (K) and ranges from warm white (1700K - 3000K) to daylight white (6500K). Neutral white (3100K - 5000K) is mainly used for general lighting applications.

The colour code is a combination of the colour rendering index (CRI) and the colour temperature (K). The first number refers to the CRI (1 = very poor colour rendering, 9 = maximum accuracy). The second and third numbers refer to the colour temperature. For example, a light with a colour code of 830 has very good colour rendering and produces a warm white light.

The colour rendering index (CRI) indicates how accurately colours are represented under a beam of light. The index goes from 1 to 99, with a CRI of 1 being the poorest and a CRI of 99 being the best possible. Be careful not to confuse colour rendering with colour temperature (K).

Lumen (lm) is the term used to describe the total amount of visible light emitted by a light source. The higher the number of lumens, the brighter it is.