The HTS separates plastics articles (Chapter 39) from rubber articles (Chapter 40) based on the primary material. Plastics are generally synthetic polymers that can be molded under heat and pressure, while rubber includes both natural and synthetic elastomers with characteristic elastic recovery. Composite articles are classified by the material that imparts the essential character, which can require a CBP ruling when both materials are present in significant proportions.

Section 301 tariffs on Chinese-origin goods have led many importers of plastics and rubber articles to diversify sourcing toward Vietnam, Thailand, Malaysia, and Mexico. However, CBP has increased scrutiny of transshipment through third countries, so importers must ensure that origin claims are substantiated by sufficient transformation in the declared country of origin.