A device for producing pipes made of thermoplastic with annular transverse profilings with a cross section in the form of undulation peaks and undulation troughs has half-molds, which complete one another pairwise along a straight mold section to form a closed mold, which can be moved in a movement direction. Projecting into the mold is an extrusion tool, which has a nozzle support body. To produce an adequate seal between the half-molds and nozzle support body, the latter is covered with exchangeably attached hollow half-shells, which form a cylindrical external face.