Explanatory notes
… square or circular cross‑section; these blocks may either be pre‑fired (baked) at about 1000 °C and then graphitised, … specific gravity or its impermeability to gases, has first been impregnated in a vacuum with tars or resins or with … these usually fall in heading 68.15 (e.g., filters, discs, bearings, moulds, acid‑resistant bricks, etc.); those of a …