Abstract: The rotor cover (2) of an open-end spinning machine possesses a projecting cover cap (3) with a side recess (4), which, on its end remote from the rotor cover is bordered by a collar (40). This possesses both in the partial zone of its circumferential area containing the collar (40), and in the remaining circumferential zone, essentially the same outer contour. The recess (4) begins, relative to the direction of rotation (f) of the spin rotor 1, between 30° and 130° after the discharge opening (50) of the fiber feed conduit (5) and ends at a section of the of the wall (51) protruding from the radial surface (20) of the rotor cover (2). The recess (4) extends to a radial surface (20) of the rotor cover (2) which radial surface (20) covers the open side of the spin rotor.