Each pure xylene isomer has its own subheading: ortho-xylene (290241), meta-xylene (290242), and para-xylene (290243). A mixture of xylene isomers that does not meet the purity threshold for any single isomer classifies under subheading 290244 for mixed xylene isomers. Purity specifications in the commercial documentation are therefore critical to correct classification.

Antidumping and countervailing duty orders have historically applied to styrene from certain origins. Trade-remedy coverage is tariff-line and origin-specific and can change as orders are initiated, revised, or revoked. Importers should check the current scope of any active orders with CBP or a licensed customs broker before shipment.