  We investigate rational maps with period one and two cluster cycles. Given
the definition of a cluster, we show that, in the case where the degree is $d$
and the cluster is fixed, the Thurston class of a rational map is fixed by the
combinatorial rotation number $\rho$ and the critical displacement $\delta$ of
the cluster cycle. The same result will also be proved in the case that the
rational map is quadratic and has a period two cluster cycle, but that the
statement is no longer true in the higher degree case.
