An upper under heading 6406 must be assembled to the point where it is recognizable as a footwear upper — typically with the component parts stitched or otherwise joined together. Unassembled cut pieces of leather or fabric generally classify under their respective material chapters rather than here.

Standard removable insoles and heel cushions designed for general footwear comfort fall under 6406. However, custom-made orthopedic appliances or therapeutic insoles may instead classify under the chapter covering medical or orthopedic devices, depending on their design and intended use. A binding ruling from CBP is advisable for borderline orthotic products.