The K-90 is a bullpup AK based upon the Polish Wz. 2005 Jantar. It is chambered in 5.56x45mm NATO and is similar but to the K-250 but was developed independently to meet different requirments. It is used by the security force for the Queen and Prime Minister of Antigua and Barbuda. It is capable of fully automatic fire, 2 round burst and semi automatic fire. It also uses 40 round magazines. The K-91 is a 7.62x51mm NATO variant most comparable to the K-251. But they were again developed independently contary to popular belief.
The K-90 LSW is a variation of the standard K-90. The modifications included a much longer 32 inch heavy barrel an integral bipod and a 150 round drum magazine. It also features a modified bolf and gas block that increase the rate of fire from 650 rounds per minute to 700 rounds per minute.