Wool tops (heading 5105) are the aligned, long-staple fiber output of the combing process, intended for worsted spinning. Noils are the short, tangled fibers removed during combing and classified as waste under heading 5103. The physical form — short, entangled, and often containing vegetable matter — is the key distinguishing characteristic, and misclassification between these headings is a common audit issue for textile importers.

Wool noils are a processed fiber byproduct and do not typically trigger USDA APHIS quarantine review the way raw fleece or animal hides might. However, if the material contains significant vegetable or soil contamination, CBP may refer the shipment for agricultural inspection. Standard commercial documentation — invoice, packing list, and certificate of origin — is generally sufficient for routine entry.