They were single-ended (controls at one end only) and had all 3 doors on the right-hand side only, in conformity with standard Zagreb (ZET) operating practices.

The TMK 101 was the first modern type of tram produced in Croatia, featuring automatic door openers, driver's and conductor's seats, electrical, air-operated, and mechanical brakes, and a protective windshield at the front.

Engineer Mandl and his team of constructors in ZET's workshops finished constructing the first prototype, No.

Three prototypes were made by ZET in their own workshops; Đuro Đaković's factory in Slavonski Brod was contracted to build the remaining 68 vehicles to ZET’s specifications, together with 110 matching trailers (which were numbered 591 to 700).

These trams have carried three different Yugoslav tramcar colour schemes, one for each of the different operators: in Zagreb they were cream-and-blue, in Osijek cream-and-red, and in Belgrade cream-and-green.