Installed on my 2003 G35 coupe, good fitment. Bolted to my custome y pipe with no flex joints 2.25 to 3 inch outlet. Definitely LOUD compared to OEM cats that sounded like birds were chirping in them. Only complaints are the fact that they don't have support brackets, but I'll probably just TIG weld on some and the welds are okay for the most part. They were not back purged while welding and have slight oxidation on the inside of the pipes. They are 2.25 OD NOT ID. NO CHECK ENGINE LIGHT THOUGH!