Small Edison screw (SES, E14) with a roughly 14mm diameter screw thread. This is the same lamp cap as commonly used in ceiling lights and table lights, although these small bulbs are not usually suitable for general lighting purposes.
These small bulbs are available in a variety of voltages and wattages to suit all common requirements. The 24v 3w version is especially popular at Christmas time as they are used in inflatable outdoor decorations.
This range also includes common oven lamps.
