5503.90 - Other:

HTS Code 5503.90 encompasses synthetic staple fibers that are not carded, combed, or otherwise processed for spinning, but which are not specifically enumerated under other headings within Chapter 55. This category serves as a residual classification for synthetic staple fibers that do not fall into the more specific categories of nylon or other polyamides (5503.10), polyesters (5503.20), acrylic or modacrylic (5503.30), or polypropylene (5503.40). Therefore, classification under 5503.90 hinges on the absence of a more precise material-based subdivision within this group of synthetic staple fibers.

The distinction from sibling categories is based solely on the material composition of the synthetic staple fiber. For instance, if the fiber is primarily composed of nylon, it would be classified under 5503.10 rather than 5503.90. Similarly, polyester staple fibers belong to 5503.20, acrylic or modacrylic to 5503.30, and polypropylene to 5503.40. This residual category is reserved for synthetic staple fibers whose primary polymer base does not align with these specifically listed materials, thus requiring careful examination of the fiber's chemical composition to ensure correct classification.

Within 5503.90, further subdivisions exist to provide more granular classification. Subcategory 5503.90.10.00 specifically covers staple fibers of vinyon, a synthetic fiber derived from vinyl chloride. All other synthetic staple fibers that meet the general criteria of not being carded, combed, or otherwise processed for spinning, and that are not of nylon, polyester, acrylic, modacrylic, polypropylene, or vinyon, will fall under the residual subcategory 5503.90.90.00. This tiered structure ensures that even less common synthetic staple fibers can be accurately classified.