0 0 0 0 0 0 0 6903.20 Retorts, crucibles, mufflers, nozzles, plugs, supports, cupels, tubes, pipes, sheaths, rods and other refractory ceramic goods, containing > 50 % alumina, or a compound of alumina and silica (excl. refractory bricks, blocks, tiles and similar refractory ceeramic constructional goods) 10