This document describes a method with two procedures for the assessment of carbon black or pigment particle and agglomerate size, and the rating of dispersion in polyolefin pipes, fittings and compounds. The method is applicable to polyolefin pipes and fittings, as well as raw material in pellet form, with the choice of procedure to be determined by the referring specification. The method is applicable to carbon black or pigmented polyolefin pipes, fittings and compounds with a carbon black content of less than 3 % by weight, and pigment content of less than 5 % by weight.