CPV code 35421100 designates Engines and engine parts for military vehicles in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
35421100 is a leaf code — the most specific level of its branch — so it can be used directly as the main CPV code of a contract notice. If it does not quite fit, check the neighbouring codes under 35421000 (Mechanical spare parts for military vehicles).