Containing, by weight, more than 50 % of alumina (al2o3) or of a mixture or compound of alumina and of silica (sio2)
Retorts, crucibles, mufflers, nozzles, plugs, supports, cupels, tubes, pipes, sheaths, rods and other refractory ceramic goods, containing, by weight, > 45% of alumina and > 50% of silica (excl. refractory bricks, blocks, tiles and similar refractory ceramic constructional goods)
Retorts, crucibles, mufflers, nozzles, plugs, supports, cupels, tubes, pipes, sheaths, rods and other refractory ceramic goods, containing, by weight, < 45% of alumina and > 50% of silica (excl. refractory bricks, blocks, tiles and similar refractory ceramic constructional goods)