Fifteen miniature cyclone presamplers were studied, each with a different combination of one of three cone lengths, three outlet tube inside diameters, and three outlet tube outside diameters. A single simple generalized equation with one constant for each cyclone accurately represented the effects of flow rate upon cut size for all 15 and also for 3 dual inlet stainless steel cyclones. Another single simple generalized equation with one constant for each cyclone accurately represented pressure drops for all. Effects of the cyclone dimensions on the constants were small. Normalized particle sizes for all 15 plotted as a single straight line from 5% to 80% efficiency when plotted on log probability paper. These equations should be useful for accurate design and prediction of performance of miniature cyclones.