The S-300FM "Fort-M" (Russian "С-300ФМ", DoD designation "SA-N-20") is another naval version of the system, installed only on the "Kirov"-class cruiser , and introduced the new 48N6 missile. It was introduced in 1990 and increased missile speed to approximately Mach 6 for a maximum target engagement speed of up to Mach 8.5, increased the warhead size to and increased the engagement range yet again to as well as opening the altitude envelope to . The new missiles also introduced the ultimate track-via-missile guidance method and brought with it the ability to intercept short-range ballistic missiles. This system makes use of the TOMB STONE MOD rather than TOP DOME radar. The export version is called the "Rif-M". Two Rif-M systems were purchased by China in 2002 and installed on the Type 051C air-defence guided missile destroyers.