Peru is a US free-trade-agreement partner under the US-Peru Trade Promotion Agreement, so qualifying goods of Peruvian origin may be eligible for preferential duty treatment, subject to applicable rules of origin. Guatemala is a beneficiary country under CAFTA-DR, which also provides preferential treatment for qualifying textile goods meeting the agreement's yarn-forward rules of origin. Importers should verify that specific shipments meet the applicable origin criteria before claiming preference.

The key distinction is whether the acrylic or modacrylic content reaches 85% or more by weight. If it does, the yarn classifies under 550931 (single) or 550932 (multiple/cabled) regardless of the secondary fiber. If it falls below 85% and wool or fine animal hair is the main secondary fiber, 550961 applies. A certified fiber composition report from the mill, specifying each fiber's percentage by weight, is the standard supporting document.