5107.10.30.00 - Of wool fiber with an average fiber diameter of 18.5 microns or less (400)

This HTS classification covers yarn spun from combed wool fibers, specifically those with an average fiber diameter of 18.5 microns or less. These yarns are intended for industrial or wholesale use and are not packaged for individual consumer sale. The "combed wool" aspect signifies a higher degree of processing, resulting in a more uniform and refined fiber structure.

Within the broader category of yarn of combed wool not put up for retail sale and containing 85 percent or more by weight of wool, this subheading specifically isolates the fine wool varieties. Its sibling category, 5107.10.60.00, encompasses "Other" combed wool yarns that do not meet the specific micron diameter criteria of this entry. Therefore, the key differentiator here is the precise measurement of the average fiber diameter, indicating a focus on particularly fine and soft wool yarns.

As this is a leaf node within the HTS, there are no further subcategories. Classification under this code is definitive once the yarn is confirmed to be combed wool, composed of 85% or more wool by weight, and possesses an average fiber diameter of 18.5 microns or less. This level of detail is crucial for accurate import and export declarations, ensuring appropriate duties and trade statistics are applied.