The FN P90 is a Belgian personal defense weapon / submachine gun manufactured by FN Herstal.
Standard P90 model.
FN P90 IR
P90 manufactured by Laserex Technologies in Australia, it projects a 4.5mW infrared laser that can only be seen with night vision equipment.
FN P90 LV
P90 manufactured by Laserex Technologies in Australia, it projects a 8mW visible laser intended to be used as a low-light shooting aid.
The P90 TR (Triple Rail), also known as the "flat-top", was introduced in late 1999. It features a Picatinny rail mounted above the receiver. It includes a full length rail on the top, and two short stumps on the sides.
FN P90 USG
The P90 USG is similar to the standard P90, but the reflex sight housing is aluminium and the sight has a revised reticle.
The standard PS90 has a long barrel and a Picatinny rail fitted on top of the receiver, lower than the standard P90 TR rail. The rail includes iron sights.
FN PS90 TR
The PS90 TR has a rail system similar to the P90 TR. As of 2013, the PS90 TR is no longer listed for sale on FNH USA.
FN PS90 USG
The PS90 USG has the same modifications to it like the P90 USG. As of 2011, it is no longer listed for sale on FNH USA, but the USG reflex sight is still offered as a standalone accessory.