The FN P90 submachine gun (SMG) was developed in the late 1980s as a defensive weapon for the troops whose primary activities does not include small arms - vehicle, tank and artillery crews. P90 may be referred as a forerunner of the PDW (Personal Defense Weapon) concept, that arose in last 4 or 5 years. FN P90 personal defense weapon is blowback operated, selective-fired weapon which fires from closed bolt. The firing is controlled by a removable trigger unit with conventional hammer.The P90 controls are completely ambidextrous, the P90 also features downward ejection of the spent cases. P90 is a bullpup design, with polymer stock, built-in reflex collimator sight with 1X magnification and reticule automatically adjustable to the light level, as well as a set of the backup open sights. The FN P90 may be equipped with a special silencer, that should be used with a special, subsonic variety of the 5.7x28mm cartridge P90 is used by Saudi Arabia, Peruan Special Forces and some special units of thailand army, and offered for export by FN.

The 5.7 x 28 mm SS190 AP ammunition is advertised as being capable to penetrate standart PAGST vest at 300 meters and standart CRISAT (kevlar + titanium) vest at 100 meters when fired from a P90