CPV code 34311120 designates Compression-ignition engines in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
34311120 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 34311100 (Internal-combustion engines for motor vehicles and motorcycles).