AVOTurboworld's Gen 3 Stainless Steel 2.5" header back exhaust for the Mazda ND models only use the highest-quality stainless steel throughout, including the laser-cut stainless steel flanges. This is a great system for customers looking for excellent sound, little drone, and expecting their exhaust to last for years and years. The exhaust tips are 3.5" tapered polished and adjustable. The system comes with a 5” body 160 cell metal cat converter. The reason for the 5” body is that it flows better than the 4” body when flowing both with comparable cells. The bigger the area within reason the more flow it will have. You might ask why 160 cell and not 100 cell like some of the aftermarket front pipes available on the market, we know that it will help with the maintenance of emissions control. The 160 cell cat converter is also a compromise between maintaining high performance and some emission control. Recommended for turbocharged or other forced induction models, however, shown to be not too loud on even NA applications where the customer wants slightly more noise from the exhaust.