Abstract: Magnetic brush development apparatus wherein flow of developer material, distributed in balance across the length of the apparatus, is assured. The apparatus includes a sump containing a supply of developer material. A magnetic brush is spaced from the sump. A feed mechanism, located within the housing between the sump portion and the magnetic brush transports developer material from the sump to the magnetic brush. A ribbon blender, located in the sump, agitates and transports developer material to the feed mechanism. The pitch of the blender blades self adjust as a function of developer imbalance. As material builds up, the blades's pitch angles decrease, reducing the rate of material transport toward areas of maximum build up. Thus, for a blender where the desired flow pattern is end-to-end, the end of the other ribbon near the end of the station toward which material is transported by the outer ribbin is self adjusting.