A crown cork is a specific closure type with a corrugated or fluted metal skirt designed to be crimped mechanically onto the lip of a glass bottle — the classic beer or soda bottle cap. Screw caps, roll-on closures, and press-fit lids do not meet this definition and fall under 830990.

Aluminum capsules used as bottle closures or decorative overwraps for wine and spirits are classified under 8309 as packing accessories, not under the aluminum articles chapter, because their function as a closure or seal is the determining characteristic. Confirm the specific end use and construction with a licensed customs broker if the article is a borderline case.