These bulbs have a bi-pin connection to lock into sockets. Often used in recessed can fixtures and track lighting, they produce a focused beam of light. They’re LED, so they last longer and are more efficient than other technologies. They also generate little heat and withstand vibration. Brightness is measured in lumens; the higher the lumens, the brighter the bulb. Bulbs with a warm light appearance have yellow tones. A bulb’s estimated yearly energy cost is based on 3 hours of usage per day at $0.11 per kWh.