These wagons are intended for the transport of containers and swap bodies.

The meaning of the characteristic letters of the Sgss wagon is "S" for a special type bogie flat wagon, "g" for a wagon used only for the transport of containers, and "ss" for a maximum speed of 120 km / h. The wagon is in the form of the only frame equipped with railway safety elements (buffers at the ends of the wagon, braking system) and positioning marks for the swap body.

These wagons, designated by the SNCF as flat wagon type S68.6, were built in 300 units in 1970/1971. They are fitted with Y25D bogies limited to 120 km / h.

These wagons are only used on whole long-distance trains between multimodal platforms (CNC or Novatrans) specially equipped for handling boxes. Vertical loading and unloading operations are carried out by gripping the boxes using grippers adapted to the characteristics of swap bodies. The swap bodies are decorated in the colors of Novatrans customers.