9902.13.51 - Socks with uppers comprising neoprene measuring 2.5 mm in thickness and covered on both sides with jersey knitted fabric of nylon; such socks with underfoots of breathable neoprene measuring 2.5 to 3 mm in thickness and covered on both sides with a jersey knitted fabric of nylon; the foregoing each formed anatomically so as to be designed for the wearer's left or right foot (provided for in subheading 6115.96.90)

This HTS category, 9902.13.51, specifically classifies specialized socks designed for athletic or protective purposes. The core defining characteristics are the materials and construction: a neoprene upper measuring 2.5 mm in thickness, covered on both sides with nylon jersey knit fabric, and an underfoot also made of breathable neoprene (2.5-3 mm thick) similarly covered in nylon jersey knit. Crucially, these socks are anatomically formed for the left or right foot, indicating a high degree of specificity in their design and intended use. This level of detail points towards items offering insulation, impact absorption, or a specific type of grip in demanding environments.

Given its placement within Chapter 99, which covers temporary legislation and modifications, this classification likely represents a temporary measure or a specific trade agreement provision applied to these particular types of socks. Unlike the broader categories of general apparel or basic footwear found in other chapters (e.g., Chapter 61 for knit apparel or Chapter 64 for footwear), 9902.13.51 is highly granular. It distinguishes itself from more general sock classifications by its advanced material composition and anatomical shaping, suggesting a specialized function beyond typical everyday hosiery. The parent context of Section XXII reinforces that this entry is not part of the standard, permanent tariff structure but rather a provision enacted under specific trade or legislative circumstances.

As a leaf node, HTS 9902.13.51 has no further subdivisions. Therefore, the classification process for items falling under this code relies entirely on meticulously matching the imported goods against the detailed description provided. Importers must verify the precise thickness of the neoprene, the type of knit fabric (nylon jersey), the double-sided covering, and the anatomical, left/right foot-specific construction. Failure to meet any of these specific criteria would necessitate reclassification into a different HTS code, potentially within Chapter 61 or Chapter 64, depending on the nature of the deviation.