The Westinghouse (MH100/U/M90/E/MED) Medium Base 100W Clear ED17 4200K HID Metal Halide Light Bulb provides efficiency and long life up to 10,000 average rated hours. Metal halide HID light bulbs produce high light output, ideal for various commercial and industrial applications where color rendering is important. For use in enclosed metal halide fixtures only, can be used for indoor and outdoor applications. This metal halide light bulb features a medium base and requires ANSI ballast M90 for correct operation. This light bulb contains mercury. Dispose of according to local, state or federal laws. Westinghouse is a trusted global brand. Westinghouse knows lighting and offers products with exceptional quality, reliability and functionality. Product reference number 37018.