Expanded metal sheets (5) are used to produce tubular filters (13). The expanded metal sheet (5) has a multiplicity of rows of openings arranged to reduce nesting when the sheet (5) is rolled on itself. In particular, the pitch between the rows of openings, the sizes of the openings, or both the pitch between the rows of openings and the sizes of the openings are varied to reduce nesting when the expanded metal sheet (5) is rolled on itself. The filters (13) can include external circumferential grooves (3), rounded corners (19) produced by a point loading process, textured surfaces (37) between openings, and/or torturous internal paths produced by non-perforated areas of an expanded metal sheet. The expanded metal sheet (5) can be composed of carbon steel coated with a material having a higher heat conductivity, e.g., tin.