Yes. Yarn 'not put up for retail sale' is typically presented in large cones, cheeses, or hanks intended for industrial use, without consumer-facing labeling or small-quantity packaging. If the same yarn is wound into small balls or skeins with retail labels, it would be classified under heading 5109 (yarn for retail sale) instead. CBP may examine packaging and labeling at entry to verify the correct heading.

Yes. The 510710 subheading covers yarn containing 85% or more wool by weight, so a blend at exactly 85% wool qualifies. Below that threshold, the yarn falls to 510720. Importers should retain fiber composition test results to support the declared subheading, particularly for blended yarns near the threshold.