The HS chapter notes define fine animal hair by species and, in some cases, by fiber diameter thresholds. Cashmere from Kashmir goats is explicitly named in 510211. Other species such as alpaca, llama, angora rabbit, and vicuña fall under 510219 as fine hair, while horse, cattle, and similar coarser fibers go to 510220. When the species is ambiguous, fiber diameter measurement and the chapter notes govern.

Belgium, Ukraine, and Portugal appear as leading suppliers because European trading houses and fiber processors often sort, clean, or re-export raw cashmere and specialty hair before it reaches the US. The country of origin for duty purposes is the country of last substantial transformation, so a fiber processed in Belgium from Central Asian cashmere may enter as a Belgian-origin product.