An apparatus (10) for changing the width of an internal die cavity (12) to accommodate product width changes has a die end plate (14) with a front surface facing the internal die cavity (12), a rear surface and defines an opening that extends through the front and rear surfaces. An internal deckle mounting block (16) attaches to the rear surface of end plate (14). An internal deckle has inner (18) and outer (20) members and mounts on the mounting block (16). Inner member (18) extends through the opening of the die end plate (14) and defines a chamber (22) and a first longitudinal slot (24). The outer member (20) is positioned about the inner member (18) concentric therewith and defines a second longitudinal slot (26). The inner member (18) rotates about the outer member (20) to vary alignment of the slots and create a passageway narrower than either slot to control coating thickness.