Gasket materials are utilized for various different types of high temperature testing to prevent leaking at bolted joints. In particular, the automotive test services field uses flanged-gasket bolted exhaust joints to provide a convenient method for installation & removal of exhaust components like catalytic converters for aging, performance testing, etc. Recent improvements in the catalyst aging methods require flanged-gasket joints that can withstand exhaust temperatures as high as 1200°C. Gasket materials previously used in these applications like the graphite based gasket materials have exhibited physical breakdowns, severe leakage, and general thermal failures under these extreme temperatures. In order to prevent these leaks, metal-reinforced gasket materials in a number of configurations were introduced to these extreme temperature environments to evaluate their robustness to these temperatures. A series of experiments were implemented to evaluate different flange and gasket material in this extreme test environment. The variables evaluated are as followed: gasket material, gasket thickness, flange material, and flange thickness. Responses evaluated were: reusability, effectiveness of seal pre/post exposure measured via cold leak rates, and the general robustness of the materials to these extreme temperatures. It was determined from this testing that in order to meet the desired leak requirements of 0.5 Lfirstname.lastname@example.orgKPa[5 psig] that 12.7 mm [½″] thick 304 stainless steel flanges and HT400 (0.080″) gasket materials would provide the best flange-gasket combination for overall robustness to extreme catalyst aging.