Abstract: A honeycomb body having a cutout, an assembly including the honeycomb body, and a method of manufacturing. The method includes forming the honeycomb body having a matrix of intersecting walls that define a plurality of cells and channels extending longitudinally through the honeycomb body. A subset of the channels are plugged to create a plurality of plugged cells in a reinforcement region of the honeycomb body. Material is removed from the honeycomb body within the reinforcement region in accordance with a peripheral shape that passes through the plugged cells to form a cutout that extends an axial depth into the honeycomb body.