Use these bulbs in small instruments, such as microscopes, projectors, and inspection lights. A raised rim on the base holds the bulb at a fixed depth to keep light properly focused. Also known as midget flange-base bulbs, they’re sized to fit tight spaces.

The trade number, printed on the bulb or in an instruction manual, makes it easy to find exact replacements.

Often used in control panels to illuminate switches, status icons, and indicators. A grooved base holds these bulbs securely in their sockets. Brightness is measured in lumens; the higher the lumens, the brighter the bulb.

Often used in automotive dashboards, instrument panels, appliances, and indicators. A flat, pinched base presses directly into the socket to hold these bulbs in place. Brightness is measured in lumens; the higher the lumens, the brighter the bulb.

Often used in signs, control panels, and elevators. Also known as telephone-base miniature light bulbs, these bulbs have a flat slide-in base to fit into older telephone switchboards, instruments, and indicators.