Abstract: A machine for blending, matting, shortening or sizing natural or artificial fibers, in which the work is performed by groups or trains of three rollers. A first working stage has a single head delivering two slivers and in which the twin bearing rollers are of large size, the two slivers emerging from the single head being fed axially or perpendicularly by directional and juxtaposing members towards a second working stage in a single lap, the width of which is at least 50% less than the width of an individual sliver. The second working stage has a reducing head which comprises a plurality of trains with twin lower retaining and traction rollers, respectively, mounted overhung on frames, adjustably spaced from one another.