Pins on the base lock these bulbs into sockets to withstand vibration. Often used in recessed can fixtures and track lighting, they produce a focused beam of light. Brightness is measured in lumens; the higher the lumens, the brighter the bulb. The bulb with a warm light appearance has yellow tones. A bulb’s estimated yearly energy cost is based on 3 hours of usage per day at $0.11 per kWh.