Abstract: A variable size deflector disc directs cooling gas to the internal surfaces of a tubular plastic film drawn between an extruder die and a pair of rollers. The disc facilitates the starting process for pulling a narrow diameter tubing from the extruder over the disc to the rollers. The plastic tub can then be readily enlarged to the final maximum diameter followed by expansion of the deflector disc to control the flow of cooling gas. The disc is preferably in the form of an iris having a plurality of pivotable leaves which can be expanded outwardly from a contracted position. The outer edge of the leaves are designed to provide a relatively smooth rounded circumference of the variable diameter disc throughout the variation in diameter between the minimum and maximum tube dimensions for the tubular plastic film process. The expandable disc permits more efficient cooling and more rapid production of the plastic film.