... Crimped Wire Mesh sets of catalytic converters, usually produced from the 304, 316,321,310 and 310 stainless steel. High nickel Stainless steel auto muffler mat ... Crimped Wire Mesh sets of catalytic converters, usually produced from the 304, 316,321,310 and 310 stainless steel. High nickel content ... especially when the converter unit located near the engine manifold. Stainless steel auto muffler mat