CPV code 31720000 designates Electromechanical equipment in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
31720000 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 31700000 (Electronic, electromechanical and electrotechnical supplies).