Section 301 measures apply at the specific 10-digit HTS line level, and applicability varies by compound. Some rare-earth compound lines under heading 2846 have been subject to Section 301 actions when originating from China, while others may have received exclusions. Importers must verify the current status of each specific tariff line against the USTR's Section 301 list before filing entry.

Mixed rare-earth compounds and oxides that do not consist predominantly of a single element typically fall under the residual subheading 284690. If the compound is predominantly cerium by weight or commercial value, 284610 may apply. For novel mixed-oxide formulations, requesting a binding ruling from CBP is the most reliable path to correct classification.