Abstract: An extrusion die is disclosed including a first member having a surface which includes a plurality of spiral channel segments formed therein and a second member having a surface which includes a plurality of spiral channel segments formed therein. The surfaces of the first and second members are positioned with respect to each other to form a leakage gap therebetween, wherein the spiral channel segments of the first and second members are mated to form a plurality of discrete spiral channels having spiral centerlines which serpentine back and forth across the leakage gap. A spiral channel is formed by a spiral channel segment in the first member aligned with a spiral channel segment in the second member, where the depths of the respective spiral channel segments are substantially 90.degree. out of phase.