The first letter of the code tells you the base or cap type of the bulb - for example, Bayonet Cap or Edison Screw Base. Tip: It is important to note whether your light fitting takes screw or bayonet type bulbs, as these are not interchangeable.

Smart Light Bulbs | Philips Hue UK

The numbers (in millimetres) tell you the diameter of the base, or the distance between the pins - for example B22, E27 or GU10 If you have bayonet light fittings and want smart bulbs that can change colour temperature, then the B22 bulb from Philips Hue is a good option. This bulb gives you both warm white and coloured light, is dimmable and can be controlled with the Hue app or voice-activated platforms. This bulb is equivalent to 60W; they’re predicted to last 25,000 hours and guaranteed for two years. The lumen output is 806lm @4,000 K. The same bulb is also available in warm white.