The importance of the nuclear potential shape in the entrance channel heavy ion collision as well as in the process of cluster formation is discussed. For more central collisions it is specially important for multiplicity distributions of intermediate mass fragments and for the parallel velocity distribution of reaction products. For peripheral collisions the entrance channel nuclear interaction is mainly responsible for the deflection angle.

PACS numbers: 25.70.Gh, 25.70.Lm, 25.70.Pq