Single synthetic filament yarns with 50 or fewer turns per meter (or untwisted) classify in the 5402.44–5402.49 group, while those twisted at more than 50 turns per meter fall in the 5402.51–5402.59 group. Accurate twist measurement from the manufacturer's technical data sheet is essential, as the boundary directly determines the applicable duty rate.

High-tenacity yarns are characterized by a tenacity exceeding a defined threshold (expressed in centinewtons per tex) and are used where tensile strength is the primary requirement, such as tire cord, ropes, and ballistic fabrics. Textured yarns have been processed — by false-twist, air-jet, or similar methods — to introduce bulk, stretch, or crimp, and are primarily used in apparel and soft furnishings. A yarn can be high-tenacity without being textured, and vice versa.