The Five-seveN pistol was designed by Fabrique Nationale of Belgium as a complimentary sidearm to the FN P90 submachine-gun. The P90 and Five-seveN share the same ammunition, the 5.7x28mm, which was developed to meet NATO requirements. The ammunition was developed to provide good penetration against modern body armor while keeping the weapons' weight, dimensions and recoil reasonable. The Five-seveN is a delayed blowback-operated, semi-automatic firearm that typically holds a 20 round magazine. Composed of a polymer frame, the Five-seveN comes with an accessory rail under the barrel. The Five-seveN is only marketed and supplied to government or law enforcement agencies only due to their uniquely devastating ammunition.