Russia sees a growth market for its Kilo class diesel electric submarines, a 30 year old design that first entered service in 1982. So far, 49 have been built, 42 are still in service and six are under construction. Russia sees foreign markets that need at least another three dozen Kilos. It may be an old design, but it is mature and has been updated with modern electronics and quieting technology (that makes it more difficult to detect under water.)
The Kilos weigh 2,300 tons (surface displacement), have six torpedo tubes and a crew of 52. They can travel about 700 kilometers under water at a quiet speed of about five kilometers an hour. Top speed underwater is 32 kilometers an hour. Kilos carry 18 torpedoes or SS-N-27 anti-ship missiles (with a range of 300 kilometers and launched underwater from the torpedo tubes.) Kilos can stay at sea 45 days at a time. It can travel at periscope depth (using a snorkel device to bring in air) for 12,000 kilometers at 12 kilometers an hour. The combination of quietness and cruise missiles makes Kilo very dangerous to American carriers. North Korea, China, India, Indonesia, Romania, Algeria, Vietnam and Iran have also bought Kilos. The main reason for purchasing Kilos is that they cost about half what equivalent Western subs go for.
The biggest potential competitor for Kilo is China, which shamelessly copies Russian military designs. The Chinese Type 39A, or Song class, looks just like the Russian Kilo. This all began in the 1990s, when the Chinese began ordering Russian Kilo class subs, then one of the latest diesel-electric design available. Russia was selling new Kilos for about $200 million each, which was about half the price other Western nations sold similar boats. Then the Chinese built two Songs, the second one an improvement on the first. These two boats have been at sea to try out the technology that was pilfered from the Russians. A third Song was built, and appears to be a bit different from the first two. The first Song appeared to be a copy of the early model Kilo (the model 877), while the second Song appeared to copy the late Kilos (model 636). The third Song boat appears to be a further evolution. Russia has warned China of trying to export these copies, in competition with the Russian originals.