Please don't mix up the different types of Tatra Waggons: The trailers of the T6A2 (motorcars) are called B6A2!
In eastern Germany (former GDR) there were mainly four different types of Tatra tramcars:
1.)
T3D (stands for "tramway, 3rd generation, release for GDR") &
B3D (stands for "beiwagen, 3rd generation, release for GDR") - all T3/B3 have a width of 2,50 meters.

T3 in Košice
2.)
T4D (stands for "tramway, 4th generation, release for GDR") &
B4D (stands for "beiwagen, 4th generation, release for GDR") - all T4/B4 have a width of 2,20 meters. The T4-generation was built on request by GDR, where tramcars with a width of 2,50m (as the T3-generation) were useable only in a few cities (like Chemnitz & Schwerin).

T4D-MT (modernized) in Dresden
3.)
KT4D (stands for "kloubova tramway, 4axles, release for GDR") - all KT4 have a width of 2,20 meters.

KT4DM (modernized) in Berlin
4.)
T6A2 (stands for "
tramway,
6th generation,
A = short version single ended, 2,
20m") &
B6A2 (stands for "
beiwagen,
6th generation,
A = short version single ended, 2,
20m") As the GDR was the main customer for that type of Tatra tramcar the "D" was unnecessary.

"Großzug" T6+T6+B6 in Magdeburg and a close up of a B6A2 tramcar.
As you can imagine there were other versions than the T6A2 in the 6th generation. Other quite popular versions were the
T6A5 (
A = short version single ended, 2,
50m") and the
T6B5 (
B = long version single ended, 2,
50m"):

T6A5 in Praha

T6B5 in Riga
Chris