Lighting buying guide
Bulb caps and fittings: E27, E14, GU10 and more
Check the exact socket marking before buying a bulb. Similar dimensions or appearance do not establish compatibility.
Guide chapters — choose a topic
Common cap markings
| Cap | Typical form | Important check |
|---|---|---|
| E27 / E14 | Screw cap; the number refers to nominal diameter in millimetres. | Exact cap size, source dimensions and fitting rating. |
| GU10 | Twist-lock cap commonly used for spotlights. | Voltage, dimensions and permitted source type. |
| GU5.3 | Two-pin cap often found on low-voltage spot sources. | Supply voltage and transformer/driver compatibility; it is not interchangeable with GU10. |
| G9 | Small loop-pin capsule. | Clearance, operating temperature and voltage specified for the source. |
| Other G / GX / special caps | Different pin spacings and constructions. | The complete marking, voltage and the manufacturer’s instructions. |
A matching cap is only the first step
- Check the rated voltage. A Philips GU5.3 source, for example, can be rated 12 V; do not infer voltage for all sources from appearance.
- Stay within the fitting’s permitted power and source requirements.
- Check bulb length, diameter and any enclosed-shade restrictions.
- Verify whether dimming is supported by both source and controls.
- Check the driver or transformer if the installation requires one.
- Choose the required lumens, colour temperature and beam angle separately.
Integrated LED and included bulbs
An integrated LED fitting may not use a replaceable bulb with one of these caps. Check the maintenance information and whether its module or driver is replaceable. A socket listed in a description does not mean a bulb is included.
Questions before buying
Can I replace a GU10 bulb with GU5.3?
No. They use different cap arrangements and may require different supplies. Do not choose by the reflector’s diameter alone.
Can I use any LED with an E27 cap?
Only if its voltage, dimensions, operating conditions, power and controls also suit the fitting.
Prepared by twoje-lampy.live · updated 24 October 2026.
Technical references: www.philips-hue.com, www.mea.lighting.philips.com.