Abstract: An air ring for supplying cooling air to a hot extruded plastic film after the film has been extruded from an annular extrusion die at an elevated temperature, has an annular body which in use surrounds the hot tubular plastic film after the film has left the extrusion die, said annular body having an annular plenum chamber to which air is supplied from an external source. A circumferentially extending series of separate air passages communicates with the plenum chamber for receiving cooling air therefrom and extending radially inwardly to respective separate orifices which in use of the air ring are adjacent to and surround the hot tubular film.