HMS 1 consists of heavy melting steel scrap containing no galvanized or blackened steel, and having a minimum thickness of 1/4 inch. Further categories include:
ISRI-200: Pieces no larger than 60 x 24 inches optimized for chargingISRI-201: Pieces no larger than 36 x 18 inches optimized for chargingISRI-202: Pieces no larger than 60 x 18 inches optimized for charging
HMS 2 consists of heavy melting steel scrap containing galvanized or blackened steel, having a minimum thickness of 1/8 inch. Further categories include:
ISRI-203: Pieces no larger than 60 x 24 inches optimized for chargingISRI-204: Pieces no larger than 36 x 18 inches optimized for charging. May include automobile scrapISRI-205: Pieces no larger than 36 x 18 inches optimized for charging. May include automobile scrap, but must be free of sheet iron or thin gauge materialISRI-206: Pieces no larger than 60 x 18 inches optimized for charging. May include automobile scrap, but must be free of sheet iron or thin gauge material