Classification of machine parts determines tariff headings based on suitability, composite function, and principal use. Parts classification follows a hierarchical rule-set: parts that are goods of the Chapters' headings (subject to stated exceptions) are classed in those headings; parts suitable solely or principally for a particular machine are classed with that machine or in specified general parts headings; parts equally suitable for certain electrical goods are allocated to a designated heading; and remaining parts fall to specified general or catch all headings. Composite or multi function machines are classified by principal function or by the single clearly defined function of their interconnected components.