Significant advances in composition and the manufacturing process have led to thin wall cordierite ceramic substrates with low thermal mass, high surface area, and large open frontal area-properties that are critical for fast light-off, high conversion efficiency and low back pressure. Indeed, such substrates are ideal catalyst supports for meeting the ever-stringent emissions regulations, ala SULEV and ULEV, as demonstrated by recent performance data1.This paper focuses on the physical durability of 400/4 and 600/4 cordierite ceramic substrates. In particular, it presents strength, fatigue, and modulus data which influence the mechanical durability. In addition, it presents thermal expansion data which impact the thermal durability. Both of these durabilities are examined as a function of operating temperature. Thus, the room temperature compressive strength data are used to assess the mechanical robustness during canning while the high temperature tensile strength and E-modulus data are used to assess the thermal shock resistance during exothermic catalytic reactions. The above data show that thin wall substrates with controlled cell geometry offer adequate robustness to meet automakers' vehicle durability requirements.