Since both converters incorporate double substrate for separate oxidation and reduction processes, the analysis was done separately for all four substrates to examine the catalysts composition and material properties. From EDX analysis, it was found that there are different loading of precious metal catalysts at the front and rear substrates. Both converters apply the same arrangement of substrates where the front one is used for reduction of NOx while the rear one is fixed for oxidation of HC and CO. Three precious metals were found to be the catalysts are Platinum (Pt), Palladium (Pd) and Rhodium (Rh). It was noticed that both converters have more concentrated Pd/ Rh combination with small amount of Pt at the front substrate and well distributed amount of those three at the rear substrate. The major element for both front and rear substrates is Pd followed by Rh and lastly Pt. Recently, Pd usage is enhanced to replace the Pt catalyst as Pd is less expensive than Pt and more resistive to sulphur in the exhaust gas which may cause catalyst poisoning.