The only techniques that can describe particle size using multiple values are microscopy or automated image analysis. An image analysis system could describe the non-spherical particle seen in figure 1 using the longest and shortest diameters, perimeter, projected area, or again by equivalent spherical diameter. When reporting a particle size distribution the most common format used even for image analysis systems is equivalent spherical diameter on the x ads and percent on the y ads. It is only for elongated or fibrous particles that the x axis is typically displayed as length rather than equivalent spherical diameter.