One rubber compound has been used to test three simple models on the operation point transfer from a VIC 125 production mixer to a VIC 1.9 laboratory mixer (scale-down), In a second step, the model which gave the best conformity in the rheological and mechanical properties of compounds and vulcanized specimen has been used for the operation point transfer tests from a VIC 1.9 laboratory mixer to a VIC 125 production mixer (scale-up), Using this model, the rheological and mechanical properties of the rubber compounds corresponded very well, The rotor clearance variation of the internal mixers proved to be a primary condition to allow this simple scale-up/down model to be successfully applied.