The objective of this study is to assess selected flexibility measures that have been presented in the literature, in an attempt to improve their applicability to support flexibility-related manufacturing decision making, and to identify missing measures. While analysing the existing variety of flexibility measurements, the paper differentiates between the extent to which a certain flexibility type is present in a system, to be measured on a 'range' or 'response' dimension, and its beneficial effect, to be assessed as a system performance. The extent of flexibility is interpreted here as a cause that eventually has a beneficial effect on the system's performance. A framework for matching the applicability of a certain flexibility measure (or assessment) to the given system's needs as encountered at a certain development stage (e.g. off-line, required, 'static' flexibility at the design stage, on-line, potential, 'dynamic' flexibility during scheduling and control), is also provided. An exposition of some engineering flexibility-related decision problems and ways to improve decisions are discussed.