Philips 140961 High Intensity Discharge High Pressure Sodium 150-Watt ED23-1/2 Mogul Base Light Bulb Philips 150-Watt HID High Pressure Sodium light bulbs offer premium light quality and energy efficiency Ideal for use in parking lots, dusk-to-dawn fixtures, roadway lighting, and industrial and commercial applications Mogul Base ED23.5 Shape C150S55 for use with ANSI S55 ballast