Heading 6903

Ceramic goods; (e.g. retorts, crucibles, muffles, nozzles, plugs, supports cupels, tubes, pipes, sheaths, rods and slide gates) excluding those of siliceous fossil meals or of similar siliceous earths

690310 Refractory ceramic goods; containing, by weight, more than 50% of free carbon, excluding those of siliceous fossil meals or similar earths 690320 Refractory ceramic goods; containing by weight more than 50% of alumina or of a mixture or compound of alumina and of silica, excluding those of siliceous fossil meals or similar earths 690390 Refractory ceramic goods; composition of which n.e.c. in heading no. 6903, other than those of siliceous fossil meals or similar earths