Hi, from our research, your 2004 Maxima has 3 catalytic converters: one left bank, one right bank, and one which is integral with the exhaust manifold. You did not indicate your state of residence. Catalytic converters are either "Federal" or "CARB" compliant. If you live in the state of CA, CO, ME, or NY, you may only legally purchase CARB-compliant converters. In addition to the OEM converters, we offer a wide range of aftermarket converters for your car which can be found at this link: https://www.carid.com/2004-nissan-maxima-catalytic-converters/