A method for forming a diesel particulate filter is presented. The method includes provided an extruder for receiving material to be extruded such extruder being configured to converting such material into a honeycomb structure having a lower portion and an upper portion. The lower portion has a bottom surface and a pair of vertically extending sidewalls terminating along outer edges of the bottom surface. The upper portion has a pair of opposing, pitched, sidewalls having lower edges terminating along upper edges of the vertically extending sidewalls and upper edges terminating along a common edge.