Leopard 2A4

The most widespread version of the Leopard 2 family, the 2A4 models included more substantial changes, including an automated fire and explosion suppression system, an all-digital fire control system able to handle new ammunition types, and improved turret with flat titanium/tungsten armour.
The Leopard 2s were manufactured in eight batches between 1985 and 1992. All the older models were also upgraded to 2A4 standard. Until 1994 Germany operated a total of 2,125 2A4s (695 newly built and the rest modified older versions), while the Netherlands had an additional 445 tanks. The 2A4 was also license manufactured in Switzerland as the Panzer 87 "Leopard" or Pz 87. This version included Swiss-built 7.5 mm Mg 87 machine guns and communications equipment, and featured improved NBC protection system. Switzerland operated 380 Pz 87 tanks.
Germany and the Netherlands found themselves with large stocks of tanks they had no need for at the end of the Cold War. These tanks were sold to NATO or friendly armies around the world. Austria (114), Canada (107), Chile (140), Denmark (51), Finland (139), Greece (183), Norway (52), Poland (128), Portugal (37), Singapore (96) Spain (108), Sweden (160), and Turkey (339) were among the buyers of the surplus tanks.
The Pz 87WE (WertErhaltung) is a Swiss modification and upgrade of the Pz 87.

The modification significantly improves protection through the addition of the Leopard 2A6M's mine protection kit, thicker armour on the front glacis, and a turret equipped with a Swiss-developed armour package using titanium alloy. The turret roof armour is improved and the smoke grenade launchers redesigned. Further improvements enhance survivability and combat capability, such as a turret electric drive similar to the Leopard 2A5, a driver rear-view camera, an independent weapons station for the loader, and enhanced command and control systems. The fire control system is also upgraded, using the Carl Zeiss Optronics GmbH PERI-R17A2 fire control system. A remote weapons station containing a fully stabilized Mg 64 0.50 calibre machine gun is also fitted to the tank.
The Pz 87-140[31] is an experimental variant of the Swiss Pz 87 with a 140 mm gun and an additional armor later used on the newer production variants.
The Leopard 2A4CHL is the upgraded Chilean version of the Leopard 2A4 ordered by Chile in 2007. Upgrades include new electronics, sighting and information systems meant to elevate the Leopard 2A4's networking capability to be equal to that of the Leopard 2A6, a new suspension system and the upgrading of the tanks main gun to the L55 smoothbore cannon used on the Leopard 2A6. Other upgrades are remote weapon stations over the gunner and commander hatches fitted with the MG3 and HK GMG. The Leopard 2A4CHL also has improved roof and side turret armour and can be uplinked with Chile's battlefield control network.[citation needed]
The Leopard 2A4M CAN is the upgraded Canadian version of the Leopard 2A4 acquired from the Royal Netherlands Army surplus. The Leopard 2A4M CAN is specially designed for the war in Afghanistan, based on experience gained by Leopard 2 operators. The first 20 were delivered in October 2010 and are being deployed to Afghanistan.[32] Though originally planned to be up-gunned to the L55 for consistency with the 2A6M CAN, the longer barreled guns (optimized for tank-vs-tank warfare) were found to be less than ideal in Afghanistan, therefore it was decided to retain the L44. In addition, only small areas of slat armour were added, in contrast with the fully caged 2A6M CANs. The protection of the Leopard 2A4M CAN has been further augmented with the addition of applique armour resembling that found on the most recent Leopard 2A7+ variant, but modified to fit the turret configuration of the 2A4.[33] Of the remaining ex-Dutch Leopards, Canada will upgrade 42 for training use (though whether they will be fully upgraded to 2A4M CAN standards is uncertain) and convert 18 to Armoured Engineering Vehicles (13 firm and 5 options). Canada has also purchased 15 2A4s from Germany as Logistic Stock Vehicles (for spare parts), and in February 2011 bought 12 2A4s/Pz 87 from the Swiss to be converted to "support vehicles" (likely Armoured Recovery Vehicles).
The Leopard 2NG (Next Generation) is a privately funded Turkish upgrade by Aselsan that includes the application of more armour (AMAP), upgraded optics and a new fire control system on the work since 1995 and to be delivered by late 2011. It was developed without an order of the Turkish Army, but might meet the requirements for the modernization of 298 Turkish Leopard 2A4.The old powerpack and the L/44 gun barrel are kept, but the combat weight is increased to 65 tonnes.According to the Turkish news sources, Finland is interested in getting the Turkish upgrade package to modernize their fleet of Leopard 2A4s.
Source:http://en.wikipedia.org/wiki/Leopard_2