When two or more fibers are present in equal proportions by weight, the HTS General Rules of Interpretation and relevant chapter notes provide tie-breaking rules — typically classifying the article according to the fiber that appears first in the applicable heading's text. In practice, this makes precise fiber testing and familiarity with chapter note hierarchy essential for accurate classification of blended synthetic garments.

For end-use statistical reporting purposes, linen, silk, and synthetic fiber apparel are grouped together in this non-wool, non-cotton category. However, at the HTS tariff-line level they are classified under distinct headings with different duty rates, so the end-use grouping should not be used as a proxy for tariff classification — each article must be classified individually based on its chief-weight fiber.