Subheadings 3
6902.10 Refractory bricks, blocks, tiles and similar refractory ceramic constructional goods; containing by weight, singly or together, more than 50% of the elements Mg, Ca or Cr, expressed as MgO, CaO or Cr2o3 6902.20 Refractory bricks, blocks, tiles and similar refractory ceramic constructional goods; containing by weight more than 50% of alumina (Al2o3), of silica (SiO2) or of a mixture or compound of these 6902.90 Refractory bricks, blocks, tiles and similar refractory ceramic constructional goods; n.e.c. in item no. 6902.1 or 6902.2