9606.21 - Of plastics, not covered with textile material:

This HTS category, 9606.21, encompasses buttons made from plastics that are not covered with textile material. It specifically includes buttons where the primary constituent material is plastic. This excludes buttons made from other materials, such as base metals (classified under 9606.22), or buttons that have a textile covering, which would fall under different HTS provisions.

The key differentiator for this classification is the absence of textile material and the presence of plastic as the principal component. This category is part of the broader heading for buttons, press-fasteners, and related articles, but focuses solely on plastic buttons.

Within this category, further distinctions are made based on the specific type of plastic or other constituent materials. The subcategories, such as those for casein, acrylic or polyester resins, and other unspecified plastic types, allow for granular classification based on the precise composition of the plastic button. This ensures accurate tariff application by recognizing variations in the raw materials used in the manufacturing of these plastic fasteners.