plastic tube extrusion machines and parts thereof, namely, air rings, bubble stabilizers, bubble collapsers, sizers, dies and die carts; plastic film extrusion machine parts, namely, secondary coolers; plastic film and sheet handling machine parts, namely, winders, slitters, perforators, cooling stations and web handling rollers; internal coolers for extruded plastic film bubbles; plastic extrusion machines and screws and polymer feeders therefor; complete blown film extrusion lines for use in plastic film manufacture; unwinders, sealers, folders and gusseters being parts of film and sheet handling and bag making machines; tarpaulin making machines; plastic film manufacturing machine parts, namely, rotating towers for gauge equalization; plastic bag making machines; complete cast film extrusion lines for use in plastic film manufacture; plastic film converting machines and plastics extruder filter screen changers