30 which is shown in section along a plane which is perpendicular to the direction of sliver feed indicated by the arrow a the guiding body 30 has four lateral guiding surfaces 30a 30b 30c and 30d and may be turned about its rotary axis m to selectively present one of the guiding surfaces 30a 30d for engagement by the running fiber bundle 5 composed of a plurality of slivers 5 39 the rotary axis m is in this example parallel to the direction of sliver feed indicated by the arrow a in the illustrated example the surface 30a is selected as the active sliver guiding surface each guiding surface 30a 30d has a different curvature as viewed perpendicularly to the sliver feed direction a the effect of the sliver guiding surface that is curved perpendicularly to the sliver feed has a spreading effect on the running sliver bundle thus while in the sliver bundle 5 the individual slivers 5 39 are close together as they run onto the sliver guiding body 30 the curved surface such as the shown active operational surface 30a cause the slivers 5 39 to separate as they run on the surface 30a the extent of separation spread of the slivers 5 39 is a function of the extent of convexity curvature of the several guiding surfaces 30a 30d thus the desired sliver spread may be obtained by selecting the appropriate surface 30a 30d to act as the operative sliver guiding surface such a selection or setting is achieved by turning the sliver guide body 30 about its rotary axis m through a suitable angle it is.