The present invention provides an extrusion die that includes a manifold transition zone that comprises a varying included angle. The varying included angle provides unparalleled freedom of design to achieve diverse fluid dynamic objectives, such as reduced residence time across the manifold width, reduced transition stagnation, improved streamlining of the mass flowing through the manifold, and reduced differential clamshell deflection across the flow channel width. The manifold may be transformed from one cross-sectional shape to another cross-sectional shape beneficially related to the varying included angle, including change from a generally extended cross-sectional shape to a generally teardrop-shaped cross-section. The manifold may include a first transition zone portion that includes the varying included angle, and a second transition zone portion that includes a constant included angle, and that is particularly beneficial for receiving an internal deckle.
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