The T-72s first major variant is as an armored bridge launcher, the MTU-72. This allows vehicles to cross ditches (often dug to hold up tanks and other vehicles). This vehicle can bridge an 18-foot ditch, and these bridges can support most armored vehicles. Another variant is the BREM series of recovery vehicles. These vehicles get a thankless job: the retrieval of damaged armored vehicles to places where they could be repaired and returned to service. It is also important.
Russia is not the only country using the T-72. This tank (or a version thereof) serves in 27 countries. Poland has been manufacturing a version of the T-72 called the PT-91 Tvardy. Like the T-72, the PT-91 uses the 125mm gun, a 12.7mm machine gun, and a coaxial 7.62mm machine gun. The PT-91 also has variants, most notably a rocket-propelled mine-clearing system. Poland is also looking to upgrade their T-72s with technology from the German Leopard 2.
Slovakia has assembled and built two versions of the T-72: The Antares, and the Moderna. The former was on par with the T-72. The latter adds the Sabca Vega thermal sight, and a commanders imager. It also swaps out the 12.7mm gun for two 20mm Oerlikon guns. The Czech Republic is upgrading its T-72s to the T-72CZ standard, with the Galileo Avionica TURMS-T computerized fire control system, reactive armor, and an Israeli engine. Romania has also built a version, the TR-125. Yugoslavia built the M-84, which was also exported to Kuwait in the aftermath of the 1990 invasion by Saddam Husseins regime. This version has also seen combat in the Balkans.
Iran is building a version of the T-72 called the Zulfiqar, which is operating alongside license-built and captured T-72s (from the Iran-Iraq War). The Zulfiqar primarily uses T-72 components (the armament suite and autoloader), but the Iranians have also used some components from the M48 and M60 tanks that formed the backbone of Irans armor force in the days of the Shah (notably the suspension) and a different engine.
The T-72s wide service (20,000 are estimated to be still be operational among the 27 countries that have acquired one version or another) will ensure it has a long career. While it is nowhere near the league of the Abrams or Challenger, it is still a cheap and reliable tank that is able to make do for countries which cannot afford a top-of-the-line tank. Harold C. Hutchison (firstname.lastname@example.org)
The T-72 has been around since 1976, and as a result, has spawned many variants. This is not unusual for tanks. The American M60 and M1 tanks, the British Challenger, Chieftain, and Scorpion, and the German Leopard have spawned variants. The chassis and powerplant of the T-72 were readily adaptable modification and upgrades. This is a good way of saving a lot money research and development cost money and time, many of the bugs in a chassis and power plant are already fixed. Operators love the reliability, bean-counters love the (relatively) low cost. A win-win situation all around. Over 50,000 T-72s have been produced in Russia, the Ukraine, Poland, the Czech Republic, and the former Yugoslavia (among other places).