EE-T1 "Osorio" main battle tank was developed in the middle of 80-ties by the largest Brazilian weapon developer "Engensa". Companies technical politics is based on wide usage of other company's providing military technologies scientific strides. Furthermore if some component reproduction license price is too high, company buys already produced components, or offer job for specialists, who took place developing one or the other element. In this way "Engensa" resolves two main problems: it's production is at a high technology level and their price is suitable even for third world countries.

Main battle tank EE-T1 "Osorio" is a good "Engensa" technical politics example. It has classical arrangement for a main battle tank and usual number of crew members. It was developed in 1985 and in 1988 it entered service in Brazilian armored forces.

The hull and the turret have differential armor. Frontal part is armored with multi-layer armor, made with included composite materials, and similar to British "chobhem" armor. Frontal armor plates are placed with a high inclination level, providing better defense.

"Osorio" armament is placed in three-seat turret. As well as EE-T1 is intended not only for Brazilian armored forces, but for export as well, it is produced with two armament variants. EE-T1 intended for Brazilian armored forces is armed with L7A3 British 105-mm rifled gun, while export modification EE-T2 is fitted with French 120-mm smoothbore gun. It also has ability to be fitted with Soviet/Russian 125-mm smoothbore gun 2A46.

105-mm main gun combat load consists from 45 projectiles, including armor-piercing, High-Explosion fitted with plastic explosives. Additional armament consists from 7.62-mm machine-gun, coaxially connected with a main gun, one more 7.62-mm anti-aircraft machine gun, placed on the roof in front of the gunner's hatch. There is ability to place 12.7-mm anti-aircraft machine gun in front of the commander's hatch.

Main gun is stabilized in two planes. It's aiming and turret rotation devices are based on electricity. "Osorio" is fitted with Belgium commander's SCS-5 and gunner's LRS-5 sights. LRS-5 is combined periscope type. It combines optical sight with day and thermo vision night channels, laser rangefinder and ballistic computer. Commander's sight differs from gunners in absence of laser rangefinder and ballistic computer. It is placed in commanders turret and connected with a main gun. Commander is able to aim and to fire independently from gunner. Tank's commander use 5 periscopes for 360 degree observation.

In the year 1987 "Engensa" finished EE-T1 export modification - EE-T2 main battle tank tests. New main battle tank was intended only for export, mostly to Near and Middle East countries. In Brazilian armored forces this main battle tank wasn't used. Mainly from EE-T1, export modification differed in 120-mm smoothbore gun instead of 105-mm placed on EE-T1, and improved fire control system.

EE-T2 "Osorio" 120-mm gun ammunition load consists from 38 projectiles with two type rounds: armor-piercing and multifunction projectile (High-Explosion fragmentation). EE-T2 fire control system differs from EE-T1. It contains WS 580-10 commander panoramic sight and gunners WS 580-19 periscope sight. Sights are developed by French company "Sfim". Both sights are made with built-in laser rangefinders, connected with ballistic computers. Sights viewing range has independent stabilization. One more "Philips" UA-9090 night vision panoramic thermal sight is mounted on the turret. It's view is projected on television screens, placed in front of gunner and commander. French specialists determined "Ozyrio's" EE-T2 hit probability into moving target: in 2 000 m range it is more than 80%.

EE-T2 secondary armament consists from 7.62-mm coaxial and 12.7-mm anti-aircraft machine guns. Like EE-T1it is also fitted with smoke grenade launchers, placed from both turret sides.

Both modification main battle tanks have the same engine and transmission built in one module. Engines are German 12-cylinder diesels MWM TBD 234 with ZF LSG 3000 transmissions. Engine block in field condition can be changed in 30 minutes.

Chassis includes 6 bearing and 3 supporting rolls from each side. Tracks are similar to "Leopard 2" main battle tank's ones, with removable rubber pads. Chassis suspension is hydro pneumatic. First, second and sixth bearing rolls are fitted with spring absorbers. Hull boards and chassis is covered with armored screens, providing additional protection against cumulative rounds.

"Osorio" has good speed and cross-country performance. It reaches 30 km/h in 10 seconds. It manages 30º slopes, 3 m wide trenches, 1.15 m vertical step. Without preparation it fords 1.2 m water obstacles.

Main battle tank is fitted with automatic fire-extinguishing system in combat and engine-transmission compartments. "Ozyrio" can be additionally fitted with Nuclear Biological Chemical protection system. This system includes air filter and individual masks for crew members, providing cleaned air. There is also ability to place special device, signalizing, when main battle tank is lightened by a laser beam.

"Osorio" standard equipment is radio set and crew communicational device.

On "Osorio" main battle tank's chassis are based later armored vehicles: self-propelled howitzer, fitted with Austrian GHN-45 155-mm howitzer; anti-aircraft defense vehicle, with coaxial 30 or 35-mm "Oerlicon" automatic guns; armored engineering vehicle; tank bridge-layer.

There is no information about "Osorio" EE-T2 serial production, however countries such as Iraq and Saudi Arabia showed interest to obtain "Osorio" for their armored forces. Brazilian requirements in EE-T1 is approximately 300 main battle tanks.