In the July 2007 START treaty data exchange, Russia gave submarines of the Project 955 class, also known as Borey, yet another name - the treaty designation of this class will be "Kasatka". If adding one more name seems confusing it is because it is. My only hope is that this name won't stick, since it is hardly used anywhere outside of the treaty context.
More significantly, the START MOU reports that the first submarine, Yuri Dolgorukiy, has 16 SLBM launchers (the missile, of course, being Bulava). Construction of the submarine was reported to be (almost) completed in April 2007. The Bulava missile, however, is not ready yet, so Yuri Dolgorukiy is listed as having 16 launchers, but no deployed missiles.
If I remember correctly, there was some uncertainty about the number of launchers on Yuri Dolgorukiy or on the next two submarines of this class that are currently under construction. As I understand it, some reports mentioned that YD has 12 launch tubes, while other submarines of this class will have full 16. I don't think this is the case - had it been, Russia would have just listed YD as carrying 12 launchers. There are no restrictions in the treaty on the number of submarine types that parties can build, so YD (had it had 12 launchers) would have been a one-of-a-kind Kasatka, while its 16-tube successors would get a different designation (say, Kasatka-M, just like Delta I and Delta II were Murena and Murena-M).