CPV code 75231220 designates Prisoner-escort services in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
75231220 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 75231200 (Services related to the detention or rehabilitation of criminals).