Edison Screw Cap
Edison Screw Cap which is Named after the inventor Thomas Edison,is used worldwide in a vast range of applications.
The most popular E27 fitting is 27mm diameter and is widely used in both the US and Europe.
The other Edison Screw Caps like the E14 is often used for smaller decorative fittings, and appliance bulbs – mostly in the UK and Europe.The E10 fitting is sometimes used in large chandeliers containing perhaps dozens of small lamps. E12 is most frequently used in the US and Canada, especially for candle bulbs. In 120-volt North America and 100-volt Japan, the standard size for general-purpose lamps is E26. The E40 is rarely used in domestic applications and is typically for lamps over 500W. This must not be confused with the extremely similar US standard 39mm diameter E39 or Mogul Screw fitting
Bulb bayonet mounts
The bayonet light bulb mount is still prevalent in many former members of the British Empire such as India, Australia, Ireland, New Zealand, the United Kingdom as well as regions of the Middle East. Older installations in countries like France also have this type of base, as well as the Edison screw (E) base used in the United States, Japan and other countries. These bulbs have two pins on opposite sides of the cap; however, some specialized bulbs have three pins.
They are used on many small incandescent light bulbs (especially halogen lamps), and on most fluorescent lights as well.The most common halogen spots are either push fit (GU4 or GU5.3), low voltage type or twist and lock (GU10 or GZ10) mains versions. PLEASE NOTE the subtle difference between GU10 and GZ10. The GU10 has a bevel around the base but the GZ10 has a square corner. This stops the GZ10 being used in a fitting designed for a GU10 but allows the GU10 to be used in either.
Below is a spotlight with GU10 base: