Under GRI 2(a) and the machinery chapters' component rules, a hydraulic cylinder imported as a separate article is classified under 841221. However, if it is imported as part of an incomplete or unassembled machine, or if it is a dedicated component presented with its host machine, it may be classified with that machine under the relevant heading. The key factors are whether the cylinder is imported separately and whether it has independent commercial use beyond a single machine application.

Tie-rod cylinders (8412210015) use external rods to hold end caps under pressure and are common in industrial and mobile equipment applications. Welded-flange cylinders (8412210030) have end caps welded or flanged directly to the barrel, offering a more compact profile suited to higher-pressure or space-constrained applications. The construction method is the controlling classification criterion, so importers should obtain manufacturer specifications confirming the cylinder body construction type.