6403.51 - Covering the ankle:

This HTS category, 6403.51, specifically encompasses footwear that has outer soles made from rubber, plastics, leather, or composition leather, and crucially, uppers constructed entirely of leather. The defining characteristic within this branch of Chapter 64 is that these are "other footwear with outer soles of leather," distinguishing them from categories that might include other sole materials or different upper constructions. Within this group, the further qualification is for footwear that "cover the ankle."

The sibling category, 6403.59, covers "other" footwear that also meets the criteria of leather uppers and leather outer soles but *does not* cover the ankle. Therefore, the primary distinction between 6403.51 and its sibling lies in the height of the footwear and whether it extends to or above the ankle bone. This height specification is a key physical attribute for classification.

The subcategories under 6403.51 provide further detail for specific types of ankle-covering footwear. For instance, 6403.51.11.00 addresses a very specific construction: footwear made on a wooden base or platform, lacking an inner sole and a protective metal toe-cap. The subsequent "Other" subcategory would then encompass all remaining ankle-covering footwear that meets the leather upper and leather sole criteria but does not fit the highly specific exclusion of the preceding subheading.