The initial production began in 2009, with the Republic of Korea Army planning to field approximately 466 units.

The K21 KNIFV's chassis is constructed entirely out of aluminium with certain parts, like hatches, made of fiberglass, reducing the weight of the vehicle and enabling it to travel at higher speeds without bulky and powerful engines.

The NIFV is to be lighter than other IFVs, including the American Bradley series, increasing both speed and payload.

The design was finally deemed production-ready in 2009, following 10 years in development and a research budget expenditure of approximately USD $80 million.

This is combined with an advanced fire-control system and gun stabilizer usually found on third-generation main battle tanks that makes the K21, together with the German Puma, able to move and engage the targets with high degree of accuracy at the same time.

The K236 MMFA (Multi-mode Fused Ammunition) has several modes including proximity, air burst, armour-piercing and fragmentation.

The mode is configured by the K21's FCS, which then transmits the necessary data to a small programmable fuse system inside the round before it is fired.

This allows more control over the trajectory and impact of the round, expanding the scope of possible targets from medium armored vehicles to aircraft and infantry personnel.

Anti-tank armament includes an indigenous 3rd-generation ATGM, with performance similar to the Israeli Spike and armour penetration of 700 to 1,000 mm (28 to 39 in) of RHA base.

It has been confirmed that the composite armour comprises S2-glass fibre and Al2O3 ceramic including lightweight aluminium alloy.

A pontoon system gives more buoyancy to float on water when additional weight is put on to the vehicle.

It has a maximum elevation of 42 degrees, allowing for a max indirect fire range of 10 km (6.2 mi).

Main armament is a 105 mm rifled low-recoil gun that fires standard NATO and newly developed smart ammunition with a max direct fire range of 4 km (2.5 mi); although the gun would not be effective against modern main battle tanks, it can defeat older tanks that North Korea still has in widespread service.

The gun can also fire the Ukrainian-designed laser-guided Falarick 105 GLATGM, which has a range of 5 km (3.1 mi) and a tandem warhead capable of penetrating 550 mm (22 in) of armor behind ERA.