6105.90 - Of other textile materials:

This HTS category, 6105.90, encompasses men's or boys' shirts that are knitted or crocheted and are made from textile materials *other than* cotton or man-made fibers. This classification acts as a residual category, capturing items not specifically provided for under the more granular subheadings within the 6105 chapter. The key differentiator here is the material composition, directing classification away from common fibers like cotton and synthetic materials.

In contrast to its siblings, 6105.10.00 (Of cotton) and 6105.20 (Of man-made fibers), this category is for shirts where cotton or man-made fibers are not the primary or predominant fiber by weight, or where the material is explicitly excluded from those other categories. Therefore, when classifying a knitted or crocheted men's or boys' shirt, if it is not primarily cotton or a man-made fiber, it will likely fall under this 6105.90 heading.

The subcategories within 6105.90 further refine the classification based on specific textile materials. These include shirts made of wool or fine animal hair (6105.90.10.00), shirts with a significant silk content (6105.90.40.00), and a residual "Other" category (6105.90.80) for any remaining textile materials not otherwise specified. The presence of these subcategories indicates the importance of precisely identifying the fiber content to ensure accurate tariff application.