5509.42.00.10 - Of polyvinyl alcohol (PVA) fibers (604)

This HTS category, 5509.42.00.10, specifically classifies multiple (folded) or cabled yarn spun from synthetic staple fibers, where the yarn contains 85 percent or more by weight of synthetic staple fibers, and crucially, these fibers are of polyvinyl alcohol (PVA). This means the yarn is constructed by twisting together two or more single yarns of PVA staple fibers, creating a more robust and often thicker thread. The "604" designation indicates a specific product or manufacturing characteristic relevant for detailed tariff application, often related to the fineness or construction of the yarn.

This classification is distinguished from its sibling, 5509.42.00.90, which covers "Other" multiple (folded) or cabled yarns meeting the same general criteria of synthetic staple fiber content but made from synthetic staple fibers *other than* polyvinyl alcohol. The key differentiator here is the precise identification of the synthetic fiber type as PVA.

As this HTS code represents a leaf node, there are no further subcategories within this specific classification. Therefore, the focus remains on accurately identifying yarn that is folded or cabled, composed of at least 85% synthetic staple fibers, and those staple fibers are exclusively polyvinyl alcohol. Classification under this code relies on the precise material composition and the construction method of the yarn.