Abstract: A rod extruded from synthetic resin material is provided which is preferred for use as a writing nib of a marker or signature pen. The rod includes an outer cylindrical shell, from the inner wall of which extend at least three stationary ribs extending radially inward therefrom and which are joined with each other on the axis of the shell and movable ribs extending radially inward from the wall and which are interleaved with the stationary ribs and which have their free end terminating adjacent to the axis of the shell. Each of the stationary and movable ribs is provided with a plurality of wings which extend circumferentially on concentric circles which are centered on the axis. The free end of each movable rib is shaped as a bulging end which is substantially circular in transverse cross section. In this manner, the rod is provided with a multiplicity of capillary passages extending in the axial direction thereof.