Stoppers made from a single piece of natural cork bark fall under heading 4503, while stoppers made from granulated or compressed cork particles bonded together are classified under heading 4504 as agglomerated cork articles. The distinction matters because the two headings can carry different duty rates.

As of current schedules, natural cork articles from Portugal, Italy, Spain, and France (all EU members) are not broadly subject to Section 301 measures, which target primarily Chinese-origin goods. However, importers should verify the specific tariff line and country of origin at the time of entry, as trade-remedy exposure can change.