Abstract: In the manufacture, for use in an optical cable element, of a tube of polymeric material, the drawn down extruded polymeric tube is annealed by causing it to travel through at least one elongate oven into which is injected, at a position intermediate of the ends of the oven, air or other gas which will have no deleterious effect on, and which is at a temperature sufficient to effect annealing of, the drawn down polymeric tube, and by directing the injected hot air or other gas on to the advancing drawn-down tube at a plurality of positions spaced along the length of the oven in such a way that turbulent flow and substantially even distribution of hot gas is provided around the advancing drawn-down tube. Use of this method of annealing enables the speed of manufacture to be at least twice the speed of manufacture hitherto achieved.