Energy losses of 0.8 MeV/atom small B n (n=<4) clusters transmitted through thin carbon foils ranging from 2 to 16 μg cm - 2 have been measured. The ratio of observed energy loss per atom of B n clusters to the energy loss of single B ions shows the enhancement at thinner foils, which indicates the vicinage effect in the cluster-solid interaction. The pulse-height defect for a cluster ion in a solid-state detector was observed.