The stock exhaust on the majority of the cars out there is very restrictive and not very performance oriented. We’re assuming that your goal is not to restrict exhaust and choke your car. Invidia has designed these 60mm catted test pipes for either your 350Z or G35. These are constructed from 304 Stainless Steel and are sure to not rust. These include O2 sensor ports. The 200cell cats will help you remain friendly to the environment while improving performance. They also include nice, large flanges to ensure a proper fit as well as 2 gaskets to make sure that exhaust gas stays where it's supposed to, inside the nonrestrictive exhaust. Because this product replaces/removes an OEM emissions control device we must state that this product is for offroad use only.