The QXL77V-750W QXL Compact Filament Halogen Lamp from Ushio was designed in conjunction with ETC's Source Four Revolution automated spotlight. The QXL (Quick eXchange Lamp) utilizes the proven performance characteristics of the 750W/77V/3250K HPL with increased lumen output. The QXL base is revolutionary in that it allows the user to\r\nquickly change the lamp without opening the fixture. This feature eliminates any issues with lamp alignment and optical settings.