Multi (three)-layer hollow parisons of large vol. for blow moulding operations are produced by bringing together the layers A.B.C. within an axially moving ring piston. The multi-layer melt expands into an annular storage space and is extruded from the nozzle by the down movement of the piston as a laminated tube. Pref. the ring piston has for each material layer an annular flow channel each connected by flow channel bores to a hinged extruder. From the funnel-shaped divergent flow channel the material enters a storage space and reaches the annular nozzle. The three layers leave as extrusion with a uniform wall thickness
