Hi Tom, I'm glad to assist you. The diameter is not noted anymore since this is a direct fit part built for a specific vehicle application. As of Magnaflow's website, only the length is noted, which is 66.2 inches long. But you can confirm fitment by entering your exact vehicle application (year, make, model, submodel and engine size) on our website's vehicle selector. After selecting the exact part that you need, the “Guaranteed to Fit, Direct fit” note/badge (in round green icon with a white check mark) would appear confirming a 100% fit. If this is good. Click the link below to order today and grab our best sale price offer, which also comes with a 30-day post-purchase price match guarantee. I hope this helps. Happy shopping. https://www.carparts.com/catalytic-converter/magnaflow/m6693302?can=CPJE1043