A device for mixing, grinding, drying, deagglomeration, crushing, or coating of feedstock with a rotor is provided, rotating around an axis within a housing, and a stator, fixed relative to the housing, encompassing the rotor with maintenance of a radial working gap. The rotor has rotor tools, which are distributed over its outer surface and whose active edges for crushing the feedstock work together with the stator tools on the inner circumference of the stator. In this regard, the feedstock is supplied in the carrier gas stream to the working gap. For effective processing of the feedstock, it is proposed according to the invention that in the outer surface of the rotor a plurality of indentations is introduced, whereby areas between two adjacent indentations form webs, which form the active edges of the rotor tools.