Abstract: An extruder for the plastification and extrusion of a rubber mixture in the form of two cold material strips through two inlet passages (4, 5) has in a housing (1) two gears (2, 3) meshing with one another in the manner of a gear pump. The inlet passages (4, 5) are provided each in an insert (8, 9) which is held replaceably in the housing (1). In this manner it becomes possible, by exchanging the inserts (8, 9) to adapt to various materials to be worked by the extruder.