in an axially extending extruder head for producing a thermoplastic tubular member , the material to be extruded is first supplied into a pair of annular first passageways spaced apart in the axial direction of the head , these passageways extend obliquely of the head axis . from the first passageways the material enters an axially elongated annular second passageway extending between the two first passageways . an annular third passage , extending transversely of the head axis , conveys the material from the second passageway into an axially extending feed passageway from which the material is extruded through the nozzle end of the head . the first , second and third passageways can be located in different parts of the extruder head .