The HTS distinguishes refractory articles partly by their alumina (Al₂O₃) content thresholds — for example, high-alumina bricks with alumina content above specified percentages fall into different subheadings than silica or basic (magnesia/chrome) refractories. Importers should obtain certified chemical analysis reports from the manufacturer to support the declared classification.

CBP may request mill certificates or laboratory analysis confirming chemical composition, technical data sheets specifying temperature ratings and density, and commercial invoices that clearly identify the refractory type and intended furnace application. For goods subject to Section 301, a detailed country-of-origin declaration and any applicable exclusion rulings should accompany the entry.