In a process for manufacturing a component for an emissions treatment unit, green ceramic product is extruded through a die to form an extrusion having a honeycomb substrate structure with an array of parallel, linear tubular cells extending along its length, the cells bounded by walls dividing adjacent cells from one another. A ceramic unit is obtained by cutting off, curing and firing a length of the extrusion a length of the extrusion. Following the firing, a mixture of a flowable, uncured curable material and a particulate metal component is injected from an end of the ceramic unit into selected ones of the cells so as to block the selected cells over at least a part of their lengths while maintaining all of the walls of the ceramic unit. The injected mixture is then cured to render it solid.