Unlike conventional tungsten-filament lamps that operate with an internal gas pressure of about one atmosphere, the Sylvania Halogen Headlight operates with an internal gas pressure of several atmospheres. This significantly reduces the rate of tungsten evaporation. The combined effects of higher pressure and the halogen cycle give halogen lamps much longer life than that of comparable non-halogen incandescent lamps operating at the same filament temperatures. This halogen lamp will also operate at higher filament temperatures with greater luminance and efficacy. The H9 is designed for internal referencing, and features world-class five axis focusing to provide optimal system precision. The low beam lamp provides high luminance and color temperature for improved nighttime visibility. It's sealed base design improves reliability, reducing maintenance costs.