A technetium-99m generator, or colloquially a technetium cow or moly cow, is a device used to extract the metastable isotope Tc of technetium from a decaying sample of molybdenum-99. Mo has a half-life of 66 hours and can be easily transported over long distances to hospitals where its decay product technetium-99m (with a half-life of only 6 hours, inconvenient for transport) is extracted and used for a variety of nuclear medicine diagnostic procedures, where its short half-life is very useful.