D-values can be thought of as a mass division diameter. It is the diameter which, when all particles in a sample are arranged in order of ascending mass, divides the sample's mass into specified percentages. The percentage mass below the diameter of interest is the number expressed after the D. The D10 diameter is the diameter at which 10% of a sample's mass is comprised of smaller particles, the D50 is the diameter at which 50% of a sample's mass is comprised of smaller particles, and the D90 is the diameter at which 90% of a sample’s mass is made up of smaller particles.