SAE J 444
This SAE Recommended Practice pertains to blast cleaning and shot peening and provides for standard cast shot and grit size numbers. For shot, this number corresponds with the opening of the nominal test sieve, in ten thousandths of inches, preceded by an S. For grit, this number corresponds with sieve designation of the nominal test sieve with the prefix G added. These sieves are in accordance with ASTM E 11.The accompanying shot and grit classifications and size designations were formulated by representatives of shot and grit suppliers, equipment manufacturers, and automotive users.