6107.99.50 - Containing 70 percent or more by weight of silk or silk waste

This HTS category, 6107.99.50, specifically classifies men's or boys' undergarments, nightwear, and similar articles, knitted or crocheted, when these items are composed of 70 percent or more by weight of silk or silk waste. This material composition is the defining characteristic for goods falling under this subheading, distinguishing them from undergarments made from other textile materials.

Unlike sibling categories such as 6107.99.10 (man-made fibers) or 6107.99.20.00 (wool or fine animal hair), this subheading focuses exclusively on the presence of silk as the primary component. The "Other" designation at the preceding level indicates that these silk-based articles are not specifically covered by any more granular prior subheadings for men's or boys' knitted or crocheted undergarments.

Within this silk-focused category, further subdivisions exist to provide greater specificity. Subcategory 6107.99.50.13 covers silk sleepwear, such as pajamas and nightshirts, while 6107.99.50.15 encompasses other silk articles that do not fall under the sleepwear classification. This distinction allows for more precise tariff application based on the intended use of the silk garment.