Column packings applicable to the field of rectification are mainly characterized by their number of theoretical stages R er meter NTSM (m(-1)), specific pressure drop per height Deltap (mbar m(-1) or Pa m(-1)), and capacity limits. A set of dimensionless numbers are derived by means of a simple model of dry gas flow within parallel plates (slit flow). Those numbers are dimensionless and able to describe measured values from various packing types and their recent improved performance only taking into account the specific surface. These numbers describe pressure drop, capacity and surface efficiency. Furthermore an approach is presented where the most important criteria describing packing performance are combined into one characteristic number to find a description within only one diagram. Examples of values from different packing types are presented. The recent developments of the 'high-performance' packings are included. Plotting these values allow extrapolation to 'expected' new packing types.