I have owned the HKS klasse for a year now and love it. Reason I am selling: Trading in my 96 328i with it's stock exhaust to bmw gallery dealership. The HKS is like new in mint condition but broken into. Very controlled sports sound. Quiet Bassy tone at Idle and aggressively growls after 4000 RPM with a bassy smooth loudness. This exhaust is not rediculously loud like a B&B. It's unique because It is loud when you want it loud and has a quiet smooth bassy tone when cruising. No resonance in car on highway.Not annoying on long drives. Resonates in car after revving past 4000 rpm, but not rediculous. Stainless Steel, with 4.5in Oval outlet. A beutiful exhaust. Have read about this exhaust in a Turbo magazine saw dyno results for up to a 12hp gain. Did notice a slight gain after installing exhaust, but never dynoed to tell if it was really a 12hp gain. If interested and have questions please email me. Selling $400 or best offer.