Abstract: Wafer processing systems and ring flow extenders used in those systems, the flow extender being proximate and around the peripheral edge of the wafer carrier. The ring flow extender has a top surface facing in the upstream direction, the ring being constructed and arranged so that when the reactor is in an operative condition, the ring closely surrounds the wafer carrier and the top surface of the ring is substantially planar and/or continuous with the top surface of the carrier. The ring flow extender has an outer peripheral surface that includes a radiused portion at or proximate to the top surface of the ring.