A polo shirt with a short placket opening at the neck classifies under heading 6105 as a knitted shirt, not under 6101 (outerwear). Heading 6101 is reserved for garments designed to be worn over other clothing, such as overcoats and anoraks. A polo shirt's construction and typical end use place it firmly in 6105.

Classification follows the chief weight of the fiber content. A shirt with 51% or more cotton by weight classifies under 610510; one with a majority of manmade fibers goes to 610520. When blends are close to 50/50, laboratory fiber-content analysis using standard AATCC or ASTM methods is the accepted method for establishing the chief weight, and importers should retain those test reports for CBP review.