The T-90S is the latest development Russian tanks and represents an increase in firepower, mobility and protection. It is manufactured by Nizhnyi Tagil of the Russian Federation. The T-90S is in service with the Russian Army and has been selected by the Indian Army, with a requirement for 250 vehicles .Three T-90S have undergone trials in the Indian and were chosen for the induction by the end of year 2000 .
The T-90S armament includes one 125 mm 2A46M smoothbore gun stabilised in two axes and fitted with a thermal sleeve. The gun tube can be replaced without dismantling inside the turret. The gun can fire a variety of ammunition including APDS (Armour Piercing Discarding Sabot),HEAT (High Explosive Anti-Tank), HE-FRAG (High Explosive Fragmentation) as well as shrapnel projectiles with time fuzes. The T-90S gun can also fire the 9M119 Refleks anti-tank guided missile system. (NATO designation AT-11 Sniper). The range of the missile is 100 - 4,000 m and takes 11.7 sec to reach maximum range. The system is intended to engage tanks fitted with ERA (Explosive Reactive Armour) as well as low-flying air targets such as helicopters, at a range of up to 5 km. The missile system fires either the 9M119 or 9M119M missiles which have semi-automatic laser beamriding guidance and a hollow charge warhead. Missile weight is 23.4 kg.
The guns automatic loader will feed both ordnance and The constituent parts of the 9M119M Laser-guided Missile. Also fitted is a coaxial 7.62 mm PKT machine gun and a 12.7 mm air defence machine gun. A 5.45 mm AKS-74 assault rifle is carried on a storage rack.
The T-90S has the 1A45T integrated fire control system (IFCS) which is automatic but with manual override for the commander. The IFCS caters for target range, four types of ammo, turning on tilt, wind velociety, atmospheric pressure, barrel wear, charge temperature, atmospheric temperature, movement of own tank towards the target and angular movement of tank.
The tank is protected by both conventional armour-plating and explosive reactive armour (ERA).
The T-90S has a fuel-injected V-85S2   (1000 hp) four-stroke V-12 piston engine. This engine can be fuelled by T-2 or TS-1 kerosene and A-72 benzine, in addition to diesel. The tank can carry up to 1,600 litres of fuel in the main fuel tanks and fuel drums. It has an enhanced maximum operating temperature i.e, 125 for the coolent. The fuel tanks are reinforced with armour plating. The tank is provided with snorkel for deep fording and can ford 5 metres of water with equipment which can be deployed in 20 minutes.
It is also fitted with ribs to mount KMT-7 mine-clearing equipment and NBC protection equipment.
The mechanical transmission includes primary reduction gear, two planetary final gearboxes and two planetary final drives. The running gear features torsion bar suspension with hydraulic shock absorbers at 1, 2 and 6 road wheel stations and tracks with rubber-metallic pin hinges..
The T-90 is fitted with the Shtora-1 defensive aids suite which is produced by Electronintorg of Russia. This system includes infrared jammer, laser warning system with four laser warning receivers, grenade discharging system which produces an aerosol screen and a computerised control system. The Indian version is likely to have the much improved Shtora-2 system.