304 SS Racing Cat-Back Exhaust System with Single Rear Exit by HKS®. Exhaust Type: Cat-Back. Exhaust Tubing Material: 304 SS. Main Tubing Diameter: 2.94". Exhaust System Sound: Aggressive / Loud. Designed for those who value maximum performance, this premium quality muffler greatly improves exhaust flow and sound. Manufactured using state-of-the-art technology and made from high-quality materials, this product will serve you for years to come.