The A'PEX Twin Chamber Blow Off Valve incorporates a arevolutionary design in boost pressure release systems. This blow of valve allows you to built up boost pressures to esape into the atmosphere when the engine is no longer under load. The result: quicker valve resonse under low and high boost pressures. This blow off valve also gives the user the ability to adjust the blow off sound. By turning a disk near the bse of the unit, the exhaust gas release volume can be adjusted to normal, loud and extra loud.