5509.21.00.00 - Single yarn (604)

This HTS classification, 5509.21.00.00, specifically covers single yarns composed of synthetic staple fibers, where polyester staple fibers constitute 85 percent or more by weight of the total content. These yarns are not packaged or presented for retail sale. This category includes yarns spun from polyester staple fibers that have been cut or broken into short lengths, forming a continuous thread. The "single yarn" designation is crucial, meaning the yarn is composed of one strand of twisted fibers and has not undergone further processes like folding or cabling.

To differentiate from its sibling, 5509.22.00, which covers multiple (folded) or cabled yarn, this category is strictly for single-ply yarns. Multiple yarns are formed by twisting together two or more single yarns, and cabled yarn involves further twisting of these multiple yarns. Therefore, the defining characteristic here is the singular construction of the yarn.

As this is a leaf node within the HTS classification structure, there are no further subcategories. Classification under 5509.21.00.00 is determined by the material composition (at least 85% polyester staple fibers), the yarn structure (single), and the presentation (not for retail sale). Examples would include bulk spun polyester yarn produced for use in textile manufacturing for weaving, knitting, or other industrial applications, but not for direct sale to consumers.