A device for dosing and mixing fluid media has a pipe (2) with an inner diameter Di (9) through which a first medium can flow, and at least two tubular means (3) arranged in the pipe (2) and having an outer diameter Da (6) for mixing a second medium with the first medium. The device is characterised in that the at least two means (3) have each one or more openings (8) through which the second medium can be mixed with the first medium, the at least two means (3) having a polygonal cross-section and being arranged in a cross-shape one behind the other in the flow direction at a distance (5) of maximum 10*Da.
