The ball-pan hardness test method has been widely used for determining degradation resistance of granulated activated carbons. This set consists of a special 8" (203mm) diameter brass-ball-pan and 15 each steel balls of 1/2" (12.7mm) and 3/8" (9.5mm) diameter. The ball-pan has a special 8mm thick hardened brass bottom plate dished out at 1092mm inner radious to give a 3.2mm thickness at its center. The bottom plate is mounted in a standard full-height sieve frame with extended rim for stacking.