These flat cars were newly developed in 1940 for the transport of heavy loads. In particular for the transport of military vehicles and tanks. The construction was characteristic: welded plate girders and profiles. They had a loading length of 8800 mm. The first delivery bore the generic markings "SSkra" and had a loading weight of 48 tons. Later, this became the new generic designation "SSy". The symbol "y" stood for a load weight of 50 tons.
After 1949, the cars were transferred to Deutsche Bundesbahn in West-Germany and Deutsche Reichsbahn in the GDR.