17 on its side opposite yarn withdrawal jet 11 connection means 17 is preferably in the form of a ferromagnetic annular disk 18 which is fitted firmly into support body 9 of conduit plate adapter 10 which is manufactured e g of aluminum or plastic support body 9 of conduit plate adapter 10 has a conical contact surface 19 which is fixed in abutment with the correspondingly conical contact surface 8 of receptacle 7 when the conduit plate adapter 10 is mounted into the fiber conduit plate 4 ejector pin 24 is fastened to disk 18 and extends partially outward through opening 25 of fiber conduit plate 4 to make it possible for conduit plate adapter 10 to be readily detached in a simple manner from fiber conduit plate 4 the precise angular fitting position of conduit plate adapter 10 can be readily achieved with positioning device 20 shown in fig2 comprising centering pin 21 fitted into the adapter 10 and a corresponding bore 22 formed in bearing disk 16 which is fixed in the bottom of receptacle 7 of the conduit plate 4 as shown in fig2 two disk shaped permanent magnets 14 14 u2032 are symmetrically arranged in the bottom of receptacle 7 and permanently anchored to fiber conduit plate 4 via bearing disk 16 which reinforces the magnetic effect the associated ferromagnetic preferably steel disk 18 forms a structural component of the support body 9 of the conduit plate adapter 10 positioned thereon such that when assembled with the fiber conduit plate 4 permanent magnets 14 14 u2032 and the ferromagnetic disk 18 are opposite each other at a.