5107.20.30.00 - Of wool fiber with an average fiber diameter of 18.5 microns or less (400)

This HTS category, 5107.20.30.00, specifically covers yarn of combed wool, not put up for retail sale, that contains less than 85 percent by weight of wool. The defining characteristic of this subcategory is that the wool fiber within the yarn must have an average fiber diameter of 18.5 microns or less. This implies a finer quality of wool, often referred to as merino or superfine wool, which commands specific pricing and end-use considerations in international trade.

At this level, the primary distinction lies in the *average fiber diameter* of the wool component. While other yarns in this chapter might be composed of wool, this particular code mandates a very fine fiber diameter. The sibling category, 5107.20.60.00, titled "Other," would encompass yarns falling under the general description of combed wool yarn (less than 85% wool, not put up for retail sale) but which do not meet the specific fine fiber diameter requirement of 18.5 microns or less.

As this is a leaf node, there are no further subcategories to introduce. The classification is complete at this point based on the material composition (less than 85% wool), presentation (not put up for retail sale), processing (combed), and a precise physical characteristic of the wool fiber (average diameter of 18.5 microns or less). Importers and exporters should ensure that documentation clearly indicates the average fiber diameter to support this specific classification.