In October Russia revealed that it had used its new “X-101” cruise missile in Syria in November 2015. The X-101/102 was previously known as the Kh-101/102. The basic information about the X-101 was similar to what was known about the Kh-101 except that the X-101 was described as being a little heavier (2.4 tons versus 2.3 tons) and with a heavier warhead (400 kg versus 364 kg) and with a longer range (4,500 kilometers versus 3,000). The increased range is questionable and the effectiveness of the stealth features are unverified.
While Russia has not introduced any new bombers since the Cold War ended in 1991, they have continued to turn out new cruise missiles. One of these missiles was the Kh-101/102, a stealthy development of the Cold War era Kh-55. The Kh-102 had been in development for nearly two decades, but most work was halted in the 1990s because of money shortages. In 2002 there were reports that work had been resumed. Then in 2007 some appeared, hanging from a Tu-95MS heavy bomber.
The Kh-101/102 began as upgrades of the Cold War era Kh-55 (AS-15) cruise missile. Then in 2007 a major upgrade, the Kh-555, appeared. This missile is six meters (19.8 feet), weighs 1.6 tons, and has a range of 3,000 kilometers. The 364 kg (800 pound) conventional warhead appears to be a cluster bomb type (carrying bomblets). The missile uses inertial and satellite supplied guidance and can hit within six meters of its aiming point. Russia says it will use these missiles to attack terrorist bases in foreign countries. There was also a nuclear version which does not appear to be in regular service.
The Kh-101/102 had a new shape, and a radar absorbing skin that made it more difficult for radar to detect it. Otherwise, the Kh-101/102 weighed 2.3 tons, but had the range and payload of the Kh-555. The Kh-102 (and the non-nuclear Kh-101) were supposed to be in service by 2013 and Russia recently stated that was when development was completed. Apparently, the Kh-102 isn't going to replace Kh-555 missiles but complement them, at least until the Kh-555s are too old to maintain and are retired. That's a process that could take a decade or more. The Kh-101/102 is also meant to give Russia a cruise missile comparable to the current American Tomahawk.
Currently, Tu-160 and Tu-95MS heavy bombers are equipped to carry a dozen Kh-555 or Kh-101/102 cruise missiles each.