The colour output of an LED bulb is measure in Kelvins. 2700k-3000k is known as Warm White, and most similar to traditional halogen bulbs. 4000k-5000k is considered Cool White, and often used in bathrooms. 6000K+ is daylight and is the brightest colour, often used in commercial applications.

The beam angle of a bulb refers to the angle of usable light emitted from a bulb. For ceiling spotlights (GU10s) a beam angle of 35-40 degrees is ideal as this is most similar to traditional halogens. Any wider angle than 60 degrees and you will find that the bright light catches your eye easily which is uncomfortable. LED bulbs such as candles and standard GLS globes bulbs are better suited to a wider beam angle, particularly if using the bulbs in lamps, so as not to have dark spots beneath the lamp. A beam angle of 300 degrees is ideal for floor and desk lamps, for ceiling and pendant lights 240 degrees will be adequate.

MR16 (otherwise known as GU5.3) MR11 and G4 are low voltage lights and are powered from a transformer. If changing these bulbs to LED, you will also need to change the transformer that powers the bulb to an LED version. All other bulbs are mains voltage and the LED equivalents are a direct replacement.