Since the expected number of passengers in express traffic in the 1930s was low and the existing tracks did not allow high axle loads anyway, the Hungarian State Railways developed a light streamlined tank locomotive. With one bogie in front and one behind, the four locomotives were allowed to travel 120 km/h in both directions. A speed of 152 km/h was reached during a test drive and in 1961, after the installation of a double blast pipe, even 160 km/h were reached. As with German streamlined locomotives, the panels were later cut out in the area of the wheels. 