Linear section of grains in polyhedral material microstructure is a system of chords. The mean length of chords is the linear grain size of the microstructure. For the prior austenite grains of low alloy structural steels. the chord length is a random variable of gamma- or logarithmic-normal distribution. https://www.chiggate.com/jerome-brown-philadelphia-eagles-mitchell-ness-1990-legacy-jersey-discount/