Abstract: One embodiment of a gas treatment device comprises: a substrate, a secondary mat support having a secondary mat basis weight, wherein the secondary mat support is disposed concentrically about at least a portion of the substrate, and a primary mat support having a primary mat basis weight, wherein the primary mat support is disposed concentrically and substantially completely about the substrate, further wherein the secondary mat basis weight is substantially less than the primary mat basis weight. One embodiment of a method for making the gas treatment device comprises: determining a first selected length for the primary mat support sufficient for the primary mat support to be disposed substantially completely about the substrate concentrically, determining a parameter of at least one subcomponent of the gas treatment device, and determining a second selected length for the secondary mat support based on the parameter.