The effect of filler networking on mechanical and electrical properties of elastomers is discussed on the basis of two models: percolation theory and kinetical cluster-cluster-aggregation. Both models imply fractal characteristics for the filler network, but differ in the predicted structure of the fractal unit cells and the dependence of the cell size xi on filler concentration. The mechanical and electrical properties of the two network models are compared to the properties of carbon black filled rubbers. It is shown that the scaling properties of the small strain modulus of N330/butyl-vulcanisates as measured by Payne agree with the predictions of the kinetical model.