The invention concerns reinforcement additives consisting of oligomeric and/or polymeric sulfur-containing organoorganooxysilanes, perhaps other unsaturated hydrocarbon-containing organoorganooxysilanes and reinforcing semiactive, active, and/or highly active carbon blacks, common in rubber, their production, and the use of the additives in perhaps silicatically filled vulcanizable rubber mixtures and compositions and in plastic mixtures or in carbon black dispersions.