The heterogeneous structure of TFR's results in high resistivities and high current noise. Accepting models of conduction in TFR's, according to which the resistivity is determined by a resistance independent of bulk-resistivity of a metallic-like component, it will be shown, that R and Ceff*(describing current noise behaviour) increase with d and d3, respectively, when d is the grain size. On the other hand, both quantities depend on the volume fraction of the metallic component in the same manner. This leads to the conclusion, that a general dependence in the form Ceff*= f(R) cannot exist.