Abstract: The mass which is made flowable (rendered plastic) must be degassed on its way to the outlet. In order to make the degassing section free of pressure a diaphragm, through which the mass flows, is provided further upstream. The extruding helix is provided with at least one helical flute, the free flow passage of which is blocked, and the diaphragm is provided with an adjustable throughput area. The diaphragm can simply consist of two perforated disks, which are rotatable with respect to each other around their axes. Each perforated disk has a fixed throughput area. The holes of both perforated disks overlap more or less, or not at all. The throughput rate of the mass through the extruding device can therefore, according to the state or the kind of mass, be regulated independently of the rotation speed of the extruding helix. Different masses can be extruded with one and the same helix, in a way hitherto not possible. One can also use an extruding helix which is shorter than was hitherto possible.