<p>The invention is a method of forming extrudate having substantially uniform thickness. A shim 33A, 33B, 33C is formed which has a thickness variation of less than or equal to about 0.5 mil 13 microns total indicated runout. This shim 33A, 33B, 33C is disposed between a first die portion 28A having a first surface 42A and a second die portion 28B having a second surface 44A. A slot 32 is formed between the first surface 42A and the second surface 44A. The slot 32 has a height dimension H substantially the same as the shim thickness. Flowable material is extruded through the slot 32.</p>
