Metal-halide lamps, a member of the high-intensity discharge (HID) family of lamps, produce high light output for their size, making them a compact, powerful, and efficient light source. By adding rare earth metal salts to the mercury vapour lamp, improved luminous efficacy and light colour is obtained. Originally created in the late 1960s for industrial use, metal-halide lamps are now available in numerous sizes and configurations for commercial and residential applications.