It was widely reported in March 2011 that a new version of the Sang-O class had been deployed in North Korea.
Satellite imagery from 2005 suggests the Sang-O II / K-300 may have been produced at the Mayang-do naval base and fitted out at the dry docks located at 39.9978 N, and 128.20019 E.
Other footage of the nearby docks of Sinp'o appear to depict the Sang-O II / K-300 as early as 2004 (at 40 01'31.20"N 128 09'55.80"E).
Subsequent satellite imagery shows the Sang-O II / K-300 deployed to the Ch’aho-rodongjagu submarine Navy Base at 40.205441 N 128.649524 E on North Korea's east coast.

According to the KPA Journal, the decision to develop a larger, improved version of the Sang-O came in the late 1990s or early 2000.
The Sang-O II / K-300 is a stretched version of the original Sang-O class with an approximate length of 39 to 40 metres and a corresponding surface displacement of approximately 300 to 340 tons.

The increased length and internal volume would suggest an increase in the operational range of the submarine and troop/equipment carrying capabilities.
Top speed is also reported to be higher in the new model, meaning an improved propulsion system is possibly housed in some of the extra length.
It was widely reported in March 2011 that a new version of the Sang-O class had been deployed in North Korea. Satellite imagery from 2005 suggests the Sang-O II / K-300 may have been produced at the Mayang-do naval base and fitted out at the dry docks located at 39.9978 N, and 128.20019 E.
Other footage of the nearby docks of Sinp'o appear to depict the Sang-O II / K-300 as early as 2004 (at 40 01'31.20"N 128 09'55.80"E). Subsequent satellite imagery shows the Sang-O II / K-300 deployed to the Ch’aho-rodongjagu submarine Navy Base at 40.205441 N 128.649524 E on North Korea's east coast.
According to the KPA Journal, the decision to develop a larger, improved version of the Sang-O came in the late 1990s or early 2000. The Sang-O II / K-300 is a stretched version of the original Sang-O class with an approximate length of 39 to 40 metres and a corresponding surface displacement of approximately 300 to 340 tons.
The increased length and internal volume would suggest an increase in the operational range of the submarine and troop/equipment carrying capabilities. Top speed is also reported to be higher in the new model, meaning an improved propulsion system is possibly housed in some of the extra length.
Sang-O-class submarine