Choosing the correct bulb holder is a fairly straightforward task, provided the bulb type is known. In U.K. domestic applications there has traditionally been a fairly limited variety of lamp-holders, with the familiar bayonet-cap B22d still reigning supreme. Although originally designed for use with incandescent filament bulbs, modern low energy alternatives such as CFL and LED types are also available for these fittings. The other most popular domestic types (incandescent and others) are the Ba15D small bayonet cap and the E27 and E14 Edison-screw types. Fluorescent fittings, excluding CFL bulbs for the above holders, are also fairly easy to identify and errors are unlikely. LED and halogen bulbs, on the other hand, are available in a wide range of different types, and if the bulb name is not known, detailed examination and measurement of the pins may be needed. Holders for the small bulbs used for indicator purposes are also made in a variety of types and sizes, and here the practical considerations of available space and accessibility needs to be taken into account, as well as the obvious matters such as voltage. The type of bulb fixing should also be suitable for the nature of the operating environment - for example, high vibration situations may require bulbs that locate very securely.