CPV code 44421500 designates Armoured or reinforced doors in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
44421500 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 44421000 (Armoured or reinforced safes, strongboxes and doors).