Classification of a fitting is based on the material of the fitting itself, not the material of the pipe or tube it connects. An aluminum fitting used to join aluminum to copper or steel pipe is still classified as an aluminum fitting under this heading, provided the fitting is itself made of aluminum.

Yes. Section 232 measures apply to aluminum articles broadly, and Section 301 measures apply to a wide range of goods of Chinese origin. Both can apply simultaneously to the same entry, and the combined duty burden should be factored into landed-cost calculations. Importers should verify the current status of both measures for the specific tariff line with a licensed customs broker.