The ASTM C664-2010 standard provides two test methods for the measurement of diffusion coating thickness. Method A determines the dimensionally varying Film thickness by measuring the difference in Film thickness between the parts before and after coating; Method B determines the total coating thickness by cross-sectional preparatory and Microscope measurements, including all included stages, regions, and layers. These methods are particularly important for dynamic systems serving at high temperatures, where diffusion coatings are continuously changing. Values in SI units in the standard are considered standard, while inch-pound units are for reference only. It is the responsibility of the user to establish appropriate safety, health and environment practices prior to use and to determine the applicability of regulatory restrictions.