  We find that tunnel junctions are not needed to provide single electron
effects in a metallic island. Eventually the tunnel junction may be replaced by
an arbitrary scatterer. It is important that even a {\it diffusive} scatterer
provides a sufficient isolation for single electron effects to persist. To
formulate this in exact terms, we derive and analyze the effective action that
describes an arbitrary scatterer. We also consider the fluctuations of the
effective charging energy.
