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 hot tubular plastic film after the film has left the extrusion die. The annular body has an annular plenum chamber to which air is supplied from an external source, and a circumferentially extending series of separate air passages communicating 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. Separate adjustors individually control the flow of air from the plenum chamber to respective air passages and associated orifices, whereby air flow from each orifice impinges on a discrete circumferentially extending portion of the tubular film in a manner substantially independently of air flow from the other orifices.