A dilution device may include a first component and a second component. The first component may define a groove including an inlet portion and an outlet portion. The second component may define an inlet in fluid communication with the inlet portion of the first component and an outlet in fluid communication with the outlet portion of the first component. Relative rotation between the first component and the second component may cause relative movement between the outlet and the outlet portion that changes the effective length of the groove fluidly coupling the inlet and the outlet of the second component. The cross-sectional area of the groove may vary along a length of the groove to provide different flow characteristics depending on the effective length of the groove.

A mixer insert for a static mixer, includes mixing elements that are arranged behind one another along a longitudinal central axis. The mixing elements have a web arrangement including a plurality of intersecting or mutually adjoining webs. The mixing elements have web arrangements that are rotated by an angle of rotation with respect to one another. The mixer insert is configured as a single-part component.