therethrough and a pair of rolls 31 withdraw the yarn plug from the tubular stuffer box the yarn plug then advances onto a cooling roll 32 and at least partially loops about same the cooling roll 32 is rotated at a slow circumferential speed it is porous and an air current is sucked through the roll from the outside to the inside thereby cooling the yarn plug 33 subsequently the yarn is again singled in that it is pulled out from the yarn plug the point of exit is indicated at numeral 34 but it should be emphasized that the point of exit is not constant due to unavoidable irregularities of the yarn plug consequently the tension of the advancing single yarn fluctuates to withdraw the yarn at the point of exit 34 a feed system 9 in accordance with the invention is used in the illustrated embodiment feed system 9 is looped at an angle of approximately 180 u00b0 the circumferential speed is more than 3 above the yarn speed as a result the yarn tension is very considerably reduced downstream of feed system 9 and the fluctuations of the yarn tension are substantially lessened a looping feed system 35 may now follow which is believed to result in a further steadying of the fluctuations in the yarn tension it is however expected that in normal cases of application the feed system 9 of the present invention will suffice to achieve a uniform result in a subsequent entanglement nozzle 16 in which an air jet is blown onto the yarn transversely of its axis which results.