Abstract: An elongate pinch housing is provided which is U-shaped in cross-section with two sidewalls and with a web wall connecting these. A pinch roller is longitudinally displaceable in these sidewalls with an annular notch at its one circumferential corner region for forming the regulation cross-section of the flexible tubing. The pinch housing in its transition region from the web wall to that sidewall which is distant from the annular notch of the pinch roller is provided with an inner, elongate side guide surface for the flexible tubing. The side guide surface projects into the pinch housing and runs inclined to its longitudinal middle plane so that the flexible tubing inserted in the pinch housing is subjected to a transverse movement.