CPV code 31712360 designates Mounted piezo-electric crystals in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
31712360 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 31712300 (Printed circuits).