This TCP 28942277-41K 289 series SpringLamp CFL features Amalgam technology which provides cooler operating temperatures for consistent performance in any position. Operating at 277 volts, this bulb fits fixtures with an E26 medium base socket. This eco-friendly bulb produces a 4100K cool white light temperature at 42 watts. With a 10,000 hour life rating, these bulbs are replaced less often than a 150-watt incandescent, making them ideal for high bay, low bay, and open lighting fixtures. Not for use in enclosed fixtures.