This High Intensity Discharge (HID) mercury vapor light bulb offers efficiency and long life up to 24,000 average rated hr. It's designed for indoor and outdoor applications, such as overhead lighting in factories, warehouses and outdoor security lighting. This mercury vapor light bulb features a medium base and requires ANSI ballast H38 for correct operation. For use in enclosed fixtures only. Westinghouse offers a full range of mercury vapor light bulbs for a variety of applications, in medium or mogul bases. These light bulbs contain mercury. Dispose of bulbs according to local, state or federal laws. Westinghouse is a trusted global brand. We know lighting and offer products with exceptional quality, reliability and functionality.