A 65% polyester / 35% cotton yarn contains less than 85% cotton by weight and is not sewing thread, so it falls under this heading (5206) rather than the high-cotton-content yarn heading (5205). The controlling factor is the cotton percentage by weight; the polyester content does not shift it to a manmade fiber yarn heading as long as cotton is the predominant fiber by weight.

A mill certificate or fiber analysis report from the manufacturer stating the percentage by weight of each fiber component is the standard supporting document. For high-value or high-volume shipments, CBP may request laboratory testing at the port of entry. Importers should retain fiber composition records as part of their entry documentation in case of a post-entry audit.