forgot to mention some makes have as many as 4 cats, some fords for example have a small pre cat up near the manifold and a small cat near the center of the exaust system, and a muffler at the end of the system. new diesels have a cat that is loaded with pms and very valuavle, old diesels have few pm and are low dollar, those inbetween have sometimes multipal cats worth varying ammounts. cars such as Jaguar, BMWs are classed as exotic and are at the top of the value list.