A 9x19mm Parabellum is a nine millimeter wide bullet. It is usually used in handguns or sub-machine 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, most notably the Glock 18. It is the standaard handgun bullet for all NATO countries.