The North Korean Najin-class frigates are some of the largest vessels in the Korean People's Navy. Although they bear a striking resemblance to ex-Soviet Kola class frigates, they are unrelated to any Russian or Chinese design. The class was originally fitted with a trainable triple 21 inch torpedo launcher, which was replaced in the mid-1980s with fixed Styx missile launchers taken from Osa class missile boats. The design is inherently dangerous, and even a minor missile failure would result in significant damage to the ship.