Raw silk (not thrown) under HTS 500200 consists of reeled filaments that have not been twisted together. Once the filaments are twisted or plied — a process called 'throwing' — the product becomes thrown silk yarn, classified under HTS 5004. The degree of twist and whether multiple threads have been combined are the key technical distinctions CBP and importers use to differentiate the two.

Switzerland functions primarily as a trading and re-export hub: Swiss-based commodity traders and textile intermediaries purchase raw silk from producing countries — notably in Asia — and re-export it globally, including to the US. Country-of-origin rules for raw silk are based on where the silk was reeled, not where it was traded, so importers must obtain accurate origin documentation from Swiss suppliers to ensure correct marking and duty treatment.