The successful conversion convinced the General Staff that similar modernization programs could be applied to other Soviet-designed tanks made in Poland and used by the Polish Armed Forces. In the late 1980s, the Polish Army modernized all of its obsolete T-55 tanks to the T-55AM Mérida standard. A total of 232 PT-91 tanks were delivered to the Polish Land Forces: 92 newly built vehicles and 140 from refurbished T-72A and T-72M1 tanks, designated PT-91M1 and PT-91MA1, respectively.

Many of the elements were used to upgrade existing fleets of T-72 tanks in countries including the Czech Republic ( T-72M4 CZ), Georgia (T-72SIM-1), and India (T-72 Ajeya Mk. Unlike many other T-72 upgrades, Polish Army PT-91s feature elements created almost exclusively by domestic companies, including the new engine, fire control system, and all communication system elements. Changes from the T-72M include a new dual-axis stabilized fire-control system, reactive armour, a more powerful engine, transmission and new automatic loader. The PT-91 was designed at the OBRUM ( Ośrodek Badawczo-Rozwojowy Urządzeń Mechanicznych, or Research and Development Centre for Mechanical Appliances) and is produced by the Bumar Łabędy company, part of the Bumar Group, a Polish technical military consortium. A development of the T-72M1, it entered service in 1995. The PT-91 Twardy ( Polish pronunciation:, English: Hard) is a Polish main battle tank.

Main battle tank blue print