GOOD OF COMMON METAL, NAMELY METAL RINGS, TUBES, PIPES, DUCTS OF METAL, ELBOWS FOR PIPES, FEEDING PIECES, BREECHES PIPES, T-PIECES, CONNECTION PIECES, PIPE JUNCTIONS, PIPE FLANGES, ADAPTER PIECES, THREADED PIPES, CLIPS FOR PIPES, PIPE MUFFS, NUTS, SHELL COUPLING PIECES, TIE PLATES, VALVES AND STRUCTURAL PARTS OF MECHANICAL VALVES; REINFORCING METAL SLEEVES, REINFORCING METAL HOSES AND REINFORCING METAL WRAPPINGS