The purpose of this standard is to establish a nationally recognized basis for checking the size of abrasive grain for use in the manufacture of grinding wheels, general polishing and other general industrial uses such as pressure blasting, lithoplate graining, etc.1) It is intended to serve as a common basis of understanding for abrasive grain producers, and for the manufacturers, distributors, and users of these abrasive products. This standard sets forth the grit size designations, the size limits and the sieves used in determining them, as well as the test procedure which is used by the industry for checking the size of abrasive grain. Abrasive grain is a natural or manufactured substance that is reduced by crushing to specific grit sizes, and is then made into products which are used for removing extraneous material by grinding, polishing, lapping, etc. Examples of some of the natural materials are corundum, emery, and garnet; manufactured materials are fused aluminum oxide and silicon carbide.