Starch-based finishing agents are applied to yarns or fabrics to improve weaveability, add body or stiffness, reduce fiber breakage during processing, or act as a temporary size that is washed out in subsequent finishing steps. Modified starches may also serve as dye carriers or fixatives. Their natural-polymer basis makes them attractive for applications where biodegradability or compatibility with natural fibers is a priority, though they are generally less durable than synthetic alternatives.

The key criterion is whether the product has a basis of amylaceous (starch or dextrin) substances. If the starch or dextrin component is the primary functional constituent, classification in 380910 is appropriate. If the product is predominantly a synthetic polymer or surfactant system with only minor starch content, heading 380991 (or another NESOI line) is more likely correct. When the formulation is a true blend with no clear dominant basis, a CBP binding ruling based on the product's technical data sheet is the most reliable path to correct classification.