Class D I of the Royal Bavarian State Railways (Königlich Bayerische Staatsbahn) was a tank locomotive with two coupled axles designed for shunting. As had been specified, these locomotives were simple and robust. They had a double-frame, with water tanks being suspended between the sole bars of the front section. Because the water capacity of 1.74 m3 soon proved too little even for a shunter operating only within the limits of its own station, additional side tanks were added to some engines during the 1880s. The outside Stephenson valve gear moved the valves on top of the horizontal cylinders. The locomotives could be braked using an Exter counterweight brake.