Fine animal hair (cashmere, angora, alpaca, vicuña, etc.) and coarse animal hair (horsehair, yak, etc.) are classified separately throughout the chapter — for example, 5102 covers coarse and fine animal hair not carded or combed, while 5108 covers yarn of fine animal hair. The distinction rests on the specific animal species and fiber diameter, and misclassification between fine and coarse can result in significantly different duty rates.

Garnetted stock — fiber recovered by mechanically shredding wool or animal hair waste — falls under heading 5104 rather than with raw wool (5101) or waste (5103). This distinction matters because garnetted stock is a recycled intermediate input with its own duty treatment, and importers sometimes misclassify it as raw fiber or waste.

The key factor is whether the wool yarn used was carded or combed before spinning. Fabrics made from carded wool yarn (typically softer, bulkier tweeds and flannels) go under 5111, while fabrics made from combed wool yarn (smoother, finer worsteds and gabardines) go under 5112. The fiber preparation stage — not the fabric's appearance — controls classification.