As it turns out, the R-29RM Sineva - a modification of the old R-29RM (SS-N-23) sea-launched missile, which recently completed flight tests from the "Ekaterinburg" submarine, now carries new warheads. The new warheads were developed by the Makeyev Design Bureau together with VNIITF/Chelyabinsk-70 (which probably indicates that they have new nuclear charge as well).

It is possible that the modification also involved changing the number of warheads that R-29RM can carry. A year ago, the defense minister, commenting on the successful launch of the R-29RM missile, mentioned that it carried three warheads, not the four that are listed in the START Treaty.