In the ASTM standards, sieve diameters are measured in inches, while millimeters are used in the ISO/BS standards. There is a slight difference between 8 inches and 200 mm or 12 inches and 300 mm diameter. In reality, 8 inches equals 203 mm and 12 inches equals 305 mm. Therefore, test sieves with a diameter of 8 inches and 200 mm cannot be nested, nor can test sieves with a diameter of 12 inches and 300 mm.