A mill designed to operate in both hot and cold modes falls under 845521 as a hot or combination hot-and-cold rolling mill. A mill built exclusively for cold reduction is classified under 845522. The determining factor is the mill's designed operating capability, not its current configuration at time of import.

Rolls for metal rolling mills have their own subheading (845530) and are classified there whether imported alone or, in some cases, with the mill. When imported as part of a complete mill assembly, classification of the whole unit versus its components should be assessed under the General Rules of Interpretation, and a binding ruling is advisable for large integrated systems.