The distinction is the manufacturing process: 7325.91 covers grinding balls produced by casting (pouring molten metal into molds), while 7326.11 covers those produced by forging or stamping. Forged balls are generally denser and harder than cast balls, and the two types serve different mill applications. Importers should obtain manufacturing process documentation from their supplier to support the correct classification, as misclassification between these two headings is a common audit finding.

Cast grinding balls of Chinese origin are subject to Section 301 additional tariffs, which has made Chinese-sourced product less price-competitive for US buyers. India has emerged as the leading alternative supplier, offering comparable product at competitive prices without the Section 301 burden. Importers should verify country of origin carefully, as grinding balls processed through third countries may still be considered Chinese-origin if substantial transformation did not occur.