The fiber composition of the hairpiece determines the heading: wigs and similar articles made of human hair fall under heading 670420, while those made of animal hair fall under 670490. Synthetic textile material wigs — made from fibers such as modacrylic, nylon, or polyester — are classified under 670419. When a wig contains a blend of human and synthetic hair, classification depends on which material gives the article its essential character, which is typically determined by the predominant fiber by weight or value.

Synthetic wigs are generally not subject to FDA regulation as medical devices unless they are specifically marketed for medical use (e.g., for chemotherapy patients) with therapeutic claims. False eyelashes made of synthetic fibers are considered cosmetic accessories and are not subject to FDA pre-market approval, though any adhesive sold with them may be subject to FDA cosmetic regulations. Standard CPSC consumer product safety requirements apply to all such articles sold in the US market.