A tube (1) of a friction bolt has an outer part (3) and an inner part (5) folded inward and a gap (7) extending in the longitudinal direction of the tube, at which gap the outer part transitions into the inner part. The lateral wall areas (9) of the inner part are flat and have a shape in which the free space between the outer and inner parts is substantially lenticular as in known tubes. The bottom (15) of the inner part lies against the outer part, and the weld (13) is arranged at a lateral offset from the plane of symmetry (11) as the area where the bottom lies against the outer part of the tube. Finally, the radii of curvature (R3) in the area of the transitions (4) from the outer part into the inner part of the tube are greater than in known tubes.