 Merino wools are normally measured on Laserscan instruments in Australia, New Zealand and South Africa, although OFDA instruments may also be used in some cases (the results from these two types of instrument are quite similar).The “coefficient of variation of fibre diameter” (CVD) is a measure of the variation in fibre fineness within the sample fleece, relative to the average fibre diameter.Crossbred and coarse wools are often measured for mean fibre diameter by older instruments—"Airflow" in many parts of the world, and even a projection microscope in some cases.