A cross-head die assembly for use with an extruder is described. The cross-head die assembly includes: an inlet section having an inlet for communicating flow from the extruder to one or more flow channels formed in a support block; and an outlet, a removably mounted die located at the outlet and in fluid communication with the one or more flow channels; said support block further comprising an interior slot extending from a first side of the support block to an outlet passageway; a removable cassette positioned in the interior slot, wherein the front end of the removable cassette is positioned to seal the outlet passageway of the slot so that the slot is isolated from the flow.