The Philips Master Color® Ceramic Metal Halide lamps are optimized for operation on High Pressure Sodium (HPS) ballasts. The ceramic discharge arc tube is more robust than the traditional quartz arc tube maintaining superior lumens with a crisp, bright, white light. These lamps are rated for open fixture use and with no shut off required, they are ideal for 24/7 operation. Simply replace the lamp at or before the end of its rated life.