The current protection of 25 ton K21 is

Frontal: Against 30mm APDS and Zis-3 76mm AP(Thanks to sloped armor and composite material)

Side/Rear: 14.5mm AP

By installing extra armor(STANAG Level VI, +40mm RHAe), it may would stop 30mm APFSDS(120mm RHAe 60° at 1.5km). pic.twitter.com/SFMdFXgXLs

— M1A2 SEPv3 Abrams (@delfoass) May 13, 2019