Russia's Improved Kilo II Submarine (Project 636.3)

Russia's original (Project 877) Kilo subs have been operating since 1980.

But the newest sub-class is the Improved Kilo II, Project 636.3. The Improved Kilo II first entered service in 2013 and is being supplied to the Russian Navy only.

The indomitable "Jive Turkey" presents a clear, well-paced, Youtube description of Improved Kilo II Project 636.6 at https://youtu.be/OIpILOFfnYM and below

Highlights of this August 2019 Youtube (usefully seen in conjunction with this list) include:

1:43 - First of class, B-261, was laid down in 2010 in St Petersburg

4:42 - list of weapons carried

5:27 - Russians are clever in the way they load torpedoes from outside through 2 torpedo tubes in the
           bow

6:02 - uses an advanced (for Russia) Lama-EKM combat system

7:10 - Rubicon-M Sonar System with details (search for Rubicon-M in this very comprehensive article
          here)

8:15 - speed, test depth, noise "117 DB AT 1/YARD" ("Jive" doesn't reveal how decibels (DB) were
          determined from 1 yard of  B-261)

8:50 - first use of Kalibr land attack missiles (against Syria) from Improved Kilo II "B-237"

9:14 - Russia's Black Sea Fleet has received its 6 Improved Kilo IIs and then the Pacific Fleet
          (see table).