12 which heats needle 12 which in turn heats filaments 40a as said filaments pass through needle 12 the fluid produces a jetting action in region 14a and passes along with the yarn 40a through passage 14b both of which exit at 14c the sudden increase in the size of the opening immediate 14c causes a zone 14f of substantial turbulence and the yarn 40b in the turbulent zone passes downstream to form an elongated generally cylindrical wad 40c within cylinder 20 of apparatus 17 the yarn wad 40c is restrained by the action of balls 30 thereon in this particular embodiment the rods 22 of cylinder 20 prevent the balls 30 from entering into yarn wad 40c since passages 32 are too small for balls 30 to pass therethrough fig2 shows the relationship between the diameter of a ball and the size of passage 32 it is pointed out that in order for apparatus 17 to function properly in restraining yarn wad 40c passage 32 must be large enough to allow a substantial portion of the surface of balls 30 to press against yarn wad 40c however it is likewise pointed out that passage 32 must be small enough to restrain the balls within the ball space 42 yarn wad 40c then proceeds into quench tube 36 in which compressed air is flowing countercurrent.