Explanatory notes
… porcelain or china 6909.12 - - Articles having a hardness equivalent to 9 or more on the Mohs scale 6909.19 - - Other … (e.g., thread guides, grinding apparatus, etc., of sintered alumina). The heading covers in particular : (1) … valves; retorts, vats, chemical baths and other static containers with single or double walls (e.g., for …