Abstract: A radial diffuser having insert rings for providing microturbulence to a paper fluid stock suspension and uniformly discharging the fluid stock via a plurality of tubes around the perimeter of the radial diffuser to a paper forming unit including a headbox. The radial diffuser comprises a cover, a main head body, an inlet feed pipe and a plurality of flexible or rigid circumferential discharge tubes. The main head body comprises either one or a pair of the co-axial ring inserts which form a fixed or variable passage or space in the chamber of the radial diffuser. The co-axial rings enhance fluid stock fiber mixing as the fluid stock flows through the radial diffuser head. The plurality of outlets around a side wall of the radial diffuser have removable housings for varying entrance coefficients to facilitate the pumping of the fluid stock suspension into the radial diffuser.