Once synthetic staple fibers have been carded, combed, or otherwise mechanically processed to align and clean the fibers for spinning, they classify under the heading for synthetic staple fibers processed for spinning rather than here. Fibers in their raw, loose, or baled state without such processing remain under this heading.

Recycled polyester staple fibers that have been re-extruded and cut to staple length generally classify here based on their current form and composition, not their origin from recycled material. However, garnetted or reclaimed fiber that has not been re-extruded may instead fall under the waste-of-manmade-fibers heading, so the processing method is the key classification factor.