- the Grad Sviyazhsk in August 2010,
- the Uglich in July 2011,
- the Veliky Ustyug in August 2011,
- the Zelyony Dol in August 2012.
- the Astrakhan in September 2006,
- the Volgodonsk in December 2011,
- the Mahachkala in December 2012.
The 100 mm A-190 gun has been retained as is the Pozitiv-ME air/surface radar.
There are also an additional 4 3M-47 Gibka (Igla-1M) short-range anti-aircraft missiles and the original 2 AK-630 Close-In-Weapon System (CIWS) have been replaced by the improved AK-630-M2.
|Class||Project 21630||Project 21631|
|Displacement||550 tons||949 tons|
|Length||62 m||74.1 m|
|Beam||9.6 m||11 m|
|Draft||2 m||2.6 m|
|Spped||29 knots||25 knots|
|Complement||29 to 26|