5510.90 - Other yarn:

This HTS category, 5510.90, encompasses "Other yarn" of artificial staple fibers, specifically those not intended for retail sale. This designation is broad and serves as a residual category for yarns that do not fit into more specific classifications based on their composition. The key distinguishing factor for classification within this heading is the primary fiber content.

Unlike its sibling categories, 5510.20 and 5510.30, which are defined by specific blending ratios primarily with wool/fine animal hair or cotton respectively, this residual category covers yarns where artificial staple fibers are the predominant component but the secondary fibers, if any, do not meet the criteria for those specific sibling classifications. For example, a yarn predominantly of artificial staple fibers mixed with a small percentage of synthetic staple fibers or other materials not explicitly mentioned in the sibling categories would likely fall under this heading.

The subcategory, 5510.90.60.00, further refines this classification by addressing yarns that are primarily composed of artificial staple fibers and are mixed mainly or solely with synthetic staple fibers. This subdivision acknowledges the prevalence of such blends in the textile industry, requiring a distinct classification to accurately capture their trade flow.