The VX6003HK features a 1/2" NPT air inlet and 12 mm orifice for increased airflow and sound levels. The more air that gets in to your horn the higher the decibel output will be. These upgraded Vortex valves have a higher air flow than the standard Kleinn valve and will make the horns louder. This kit can also make Kleinn horns compatible with higher pressure air systems. The kit includes the upgraded valve, 12 ft of 1/2" tube, and the necessary fittings and adapters.