9" length! Are you sure about that? There are three measurements: the base outside diameter, the top outside diameter, and the height (length). I didn't see any filters close to that length on the K&N site when matching up to a Mazda CAI. I want to get a filter that is close (or exact) in size because a smaller filter means less airflow. A 5" versus a 9" with the other two dimensions the same is a massive difference.