Duty exemption for ball bearings: initial clearances exempt subject to aggregate threshold, declarations and brand exclusions. Exemption from excise duty applies to clearances of ball or roller bearings under Chapter 84 for initial clearances up to an aggregate annual threshold and to specified goods used as inputs for further manufacture within the producing factory, subject to aggregation across factories and manufacturers, exclusions for goods bearing another person's brand name, and procedural requirements including a declaration and undertaking where there were no prior-year clearances.