Dinan engineers designed the F30 335i and F32 435i exhaust to improve exhaust flow by reducing back pressure, resulting in increased power output and a great sporty sound that is civilized when you want it to be, and pleasantly aggressive under hard acceleration. Dinan also incorporates a Helmholtz chamber design that reduces resonance or"drone" at low RPM. The system is built to exacting specifications to ensure the perfect fit using the factory hangers. It is made from 100% 16 gauge 304 stainless steel and will resist corrosion for years to come. The design features twin 3.5" polished stainless, or ceramic black, exhaust tips for a tasteful, high-performance look. The factory computer-controlled exhaust valve is eliminated.