17 sealing, packing and insulation material; non-metallic flexible pipes, stuffing box and flange gaskets, packing cones, valve rings, steam valves, butterfly valves, packing plates, valves, packing rings, sealing rings, cord rings, oil and grease rings, dust rings, gauge rings, coupling discs, hoses, pipes and tubes, fittings, hose pipe and pipe clamps, belt connectors, flanges, bends; flange gaskets not of metal