The thickness of the bands used in targets for CYLMIX experiments is an important experimental parameter. This measurement becomes difficult because the peak-to-valley surface roughness is at least 10% of the band thickness. Therefore, a method had to be devised that would accurately represent the band thickness and include the statistical nature of the very rough surface. The Effective Density was the parameter chosen to give a good representation of the band thickness. This paper describes how to make this measurement and how it was used in recent CYLMIX experiments.