HTS code 9902.13.27 covers "Flame resistant viscose rayon fibers suitable for yarn spinning, with minimum fiber tenacity of 25 cN/tex, based on modal fiber derived from beechwood and containing 20 to 22 percent by weight of phosphorus-based flame retardant agent (provided for in subheading 5504.10.00)" under the US Harmonized Tariff Schedule. This is the official duty rate charged by US Customs when this product is imported into the United States, sourced directly from the U.S. International Trade Commission and refreshed daily.