Gray cast iron trench grating / solid covers and frames shall be as manufactured by Mingda. Gray cast iron used in the manufacture of trench grating or solid covers and frames shall conform to ASTM A48-83 CLASS 35. All castings shall be of uniform quality, free from blow holes, shrinkage defects, swells, cracks or other defects. Casting will be free of fins, burrs and slag. Ductile cast iron trench grating or solid covers (frames furnished in gray cast iron unless specified ductile cast iron) shall be as furnished by Mingda. Ductile cast iron used in the manufacture of trench grating or solid covers and frames shall conform to ASTM A536-80 grade 65-45-12. All castings shall be of uniform quality, free from blow holes, shrinkage defects, swells, cracks, or other defects. Casting will be free of fins, burrs and slag.