Wet spinning — where flax fibers pass through hot water during drafting — produces finer, smoother yarn suitable for high-quality apparel and fine linen fabrics. Dry spinning yields a coarser, hairier yarn used in industrial textiles, canvas, and coarser home furnishing fabrics. The distinction affects both price and end-use suitability, and at the HTS level the two processes may be captured in separate subheadings based on yarn count.

Flax yarn must be marked with its country of origin in accordance with standard CBP marking rules for textile products. If the yarn will be further processed into fabric or finished goods in the US, the origin of the yarn itself must be traceable for purposes of textile quota monitoring and any applicable trade preference claims. Fiber content labeling requirements under the Textile Fiber Products Identification Act apply to downstream consumer products incorporating the yarn.