Abstract: An extrusion die has first and second die bodies that define an extrusion cavity therebetween. The extrusion cavity has an inlet, a primary manifold that extends from the inlet along a flow direction, and an outlet that defines an elongate slot. In some examples, cavity has an intermediate chamber that extends from the primary manifold along the flow direction, the intermediate chamber having a back line and a front line that taper away from one another as they extend outwards towards opposing ends of the die. The primary manifold has a front end portion that is defined between opposing inner surfaces, at least one of inner surface tapering towards the other as it extends along the flow direction. In some examples, the inner surface has first and second curved portions that curve to provide a smoother transition from the primary manifold to a downstream chamber of the extrusion cavity.