A fiber supply tube for disentangled fiber material that is to be transported by compressed air flow or suction through said tube, wherein said tube has a circular arc over a portion of its length, and wherein an angle α of curvature or directional change of said circular arc is in the range of 95 to 105° and has a ratio relative to a radius of curvature (r) of a center line of said tube of α/r=2.5 to 3.5 wherein said radius of curvature (r) has a magnitude of 30 to 40 mm, and
- wherein said circular arc has an inner diameter that decreases continuously from 8 mm to 6 mm.