Parts that are identifiable as suitable for use solely or principally with a specific machine are generally classified with that machine under the relevant heading. Heading 8487 applies only when no more specific heading covers the part — it is a true residual. Always check the Section XVI notes and the specific machine heading before defaulting to 8487.

848710 specifically covers ships' and boats' propellers and their blades, so most marine propellers land here. However, propellers for aircraft fall under the aviation chapter, and very small propellers for model craft may be classified differently depending on their principal use. The key criterion is that the article is designed for a ship or boat.