Adjustable iron sights, optional mount required for optical sights
The Zastava M90 is an assault rifle developed and produced by then Yugoslavian, nowadays Serbian Zastava Arms. It was developed from the famous Zastava M70 assault rifle, the modified copy of the Soviet AKM assault rifle, but with a Western type flash eliminator added on the barrel end, chambered in also Western, 5.56x45mm caliber, and with that a different magazine design, similar to Western STANAG magazine
The M90 was intended to be a weapon that will replace the M70 in Yugoslav People's Army, but the breakup of Yugoslavia disrupted the production and the weapon today remains rare and was never actually formally used by anyone, probably due to lack of 5.56x45mm ammunition.
The Zastava M90 is actually the improved M70, chambered in Western 5.56x45mm NATO round, also comes with a flash eliminator and different magazine design, which means that like its predecessor, the M90 is an modified Soviet AKM. It is gas-operated, air-cooled and magazine-fed, shoulder fired weapon with selective fire capability, and like M70, can launch rifle grenades and has a rifle grenade sight added on the gas tube, instead of under barrel grenade launcher like on most other AK variants.
Like all Zastava produces AK variants, the M90 can be identified from the originals by its longer lower wooden handguard design, which has three cooling vents, no bulge and like the stock, is made out of different wood type. Also, due to using Western round, this particular model also has different magazine design, similar to Western STANAG and interestingly, a Western type flash eliminator, similar to one used on American M16 assault rifle. Like on the other Zastava AK's, this three vent feature gives the M90 lower overheating when compared to the originals, but, the Western round in this case, slightly reduces reliability.