Explanatory notes
… by weight, singly or together, more than 50 % of the elements Mg, Ca or Cr, or expressed as MgO, CaO or Cr 2 O 3 … kilns, furnaces or other plant for the metallurgical, chemical, ceramic, glass and other industries. It includes, … of all shapes (parallelepiped, wedge shaped, cylindrical, semi-cylindrical, etc.), including keystones and other …