CPV code 44166000 designates Oil country tubular goods in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
44166000 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 44160000 (Pipeline, piping, pipes, casing, tubing and related items).