Subheadings 3
6903.10 Refractory ceramic goods; containing, by weight, more than 50% of free carbon, excluding those of siliceous fossil meals or similar earths 6903.20 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 6903.90 Refractory ceramic goods; composition of which n.e.c. in heading no. 6903, other than those of siliceous fossil meals or similar earths