Teat cup liners designed specifically for milking machine clusters are generally classified as parts of milking machines rather than under a general rubber-goods heading, because their design is dedicated to a specific machine function. Supporting documentation such as OEM part numbers or technical drawings showing the liner's fit within a milking cluster strengthens this classification.

Each line item in a mixed shipment should be classified individually based on the machine it is designed for. Parts identifiable as milking machine components and parts identifiable as dairy processing machinery components both fall under this heading, so a mixed shipment may consolidate under a single classification — but the commercial invoice should itemize each part type separately to facilitate accurate entry and potential audit review.