A 9x19mm Parabellum is a nine millimeter wide bullet. It is usually used in handguns or submachine guns. The nine millimeter is often referred to as a "nine", "9mm", or "9x19". It is one of the most widely used bullets in history originating with the 9x19 Luger, invented in Germany. Many guns fire the 9mm, including the Sten Mk II and Glock 18. It is the standard handgun bullet for all NATO countries.