Super Sound Master Series 304 SS Cat-Back Exhaust System by HKS®. Sound (Close): 93 dB. Sound (Idle): 62 dB. Tubing: 2.4″-2″ x 2. Tip Style: RS. Tip Size: 4″. Professionally developed with a racer in mind, this HKS exhaust system provides an easy opportunity to upgrade both the horsepower and sound of your precious vehicle. Made from first class materials, it will serve you for years to come.