Rock wool (stone wool) and slag wool — fibrous insulation produced by spinning molten mineral or industrial slag — are primary thermal and acoustic insulation materials in commercial construction, industrial pipe insulation, and fire-protection assemblies. The US tariff schedule is notably granular here, with dedicated lines for acoustic pads and boards (6806100010), narrow batts not over 61 cm wide (6806100020), wider batts (6806100040), pipe coverings (6806100060), and other bulk or roll forms (6806100090). Canada leads US imports under this heading, consistent with cross-border construction supply chains, with Mexico and the United Kingdom also significant sources. Importers should classify by physical form and end-use configuration, as the distinction between acoustic, thermal, and pipe-covering products determines the correct 10-digit line.

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