Refractory bricks, blocks, tiles and similar refractory ceramic constructional goods; n.e.c. in item no. 6902.1 or 6902.2

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

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