Metal halide lamps also known as HID, arc or discharge lamps consist of an internal quartz glass arc tube usually within an outer envelope. Typically metal halide lamps require a ballast or driver and ignition system to supply a high starting voltage to get the arc to light up. Metal halides feature two electrodes in which an arc of light is formed once the lamp is ignited. Metal halides can produce a very focused and intense light output. With different high pressure gas mixtures and chemicals, it is possible to achieve various levels of high CRI, different color temperatures and life expectancy.