Classification rules generally require that a part be identifiable by its shape, construction, or design as suitable for use principally or solely with a specific type of machinery. If a component is clearly engineered for textile fiber or yarn production equipment — for example, a specialized card flat or a spindle whorl — it belongs here. A generic fastener or bearing with no textile-specific design would typically fall under general machinery parts headings. Consulting a licensed customs broker is advisable when the part's design is ambiguous.

Rebuilt or reconditioned parts are generally classified by their essential character and function, not their condition, so they typically fall under the same heading as new equivalents. However, condition may affect valuation, and some trade-remedy orders specify whether they apply to rebuilt components. Importers should also check whether the country of origin of the rebuilt part is the country where the rebuilding occurred or where the original part was manufactured, as this can affect duty and trade-remedy exposure.