5506 - Synthetic staple fibers, carded, combed or otherwise processed for spinning:

Heading 5506 encompasses synthetic staple fibers that have undergone further processing beyond their initial extrusion. This processing includes carding, combing, or other treatments specifically designed to prepare the fibers for spinning into yarn. The key distinction of this heading lies in the post-extrusion mechanical treatments that orient and align the fibers, making them suitable for textile manufacturing.

Unlike other categories at the Section XI level, which might cover natural fibers, yarns, fabrics, or made-up articles, heading 5506 is exclusively focused on the intermediate stage of processed synthetic staple fibers. Its sibling categories would generally cover different forms of textile materials, such as raw fibers, yarns, or woven/knitted goods, and are not defined by the specific carded or combed nature of synthetic staple fibers.

The subcategories within 5506 further differentiate these processed fibers based on their polymer composition. This allows for precise classification by material type, such as nylon or other polyamides (5506.10), polyesters (5506.20), acrylic or modacrylic fibers (5506.30), and polypropylene (5506.40). The residual category, 5506.90, captures all other synthetic staple fibers processed in a similar manner but not falling into the enumerated polymer groups.