Section 13 Articles of stone, plaster,cement,asbestos, mica or similar materials; ceramic products; glass and glassware 69 Ceramic products 69 03 Other refractory ceramic goods (for example, retorts, crucibles, muffles, nozzles, plugs, supports, cupels, tubes, pipes, sheaths and rods), other than those of siliceous fossil meals or of similar siliceous earths Commodity Code Description 69 03 10 - Containing by weight more than 50 % of free carbon 69 03 20 - Containing by weight more than 50% of alumina (A12O3) or of a mixture or compound of alumina and of silica (SiO2) 69 03 90 - Other