Once nylon/polyamide (65151) and polyester (65152) are excluded, the NES category most commonly captures polypropylene filament yarn, polyethylene filament yarn, and specialty copolymer or elastomeric filament yarns that have been textured. Acrylic filament yarn may also appear here depending on the specific classification schedule. Importers should obtain a fiber composition certificate from the manufacturer to confirm the correct heading.

For blended synthetic filament yarns, classification generally follows the fiber that predominates by weight. If polyester is the chief weight component, the yarn would typically be classified under the polyester heading (65152) rather than the NES heading. When no single fiber predominates, or when the blend involves a fiber not specifically named in the schedule, the NES heading (65159) may apply — but a binding ruling from CBP is advisable for recurring shipments of complex blends.