The Bavarian CL Bay 06b was a short open coach for branch line services with the Royal Bavarian State Railways (k.Bay.Sts.B.). It was listed in their 1913 fleet register under Design Sheet No. 570.

With the growth of the branch line network in the Kingdom of Bavaria, there was a need for suitable coaches on the so-called Lokalbahnen or local railway lines. Since the only available locomotives were tank engines with low tractive power, such as the Class PtL 2/2, passenger coaches of a particularly light design were required. These coaches were not suitable for military transport.

Between 1905 and 1911 a total of 281^[1][2] wagons of classes BL, BCL, CL and PPostL were procured, all of which - except for the wagons of Class PPostL - had a uniform floor plan, open platforms at each end with Dixi gates on the steps and gangways only protected by a single iron railing. Large window panes were fitted instead of the composite windows that had been usual up to that point. They are sometimes referred to as 'the shorts' or 'the short ones' (Die Kurze).

Between 1906 and 1909, 74 of these wagons, built to the specifications of Design Sheet 570, were procured in a total of five batches from the company of Waggonfabrik Josef Rathgeber in Munich. In contrast to the CL based on Sheet 569, these had a service compartment for the guard.

Four coaches were retired by 1939. After the end of the Second World War in 1945, the location of other new coaches could no longer be ascertained. Of the vehicles delivered, 51 entered DB service, where they were decommissioned by 1960.

The following coaches were also built for the Lokalbahn branch line network:

• BCL Bay 09, long passenger coach
• CL Bay 11a, long passenger coach
• GwL, branch line goods van
• PwPost Bay 06, mail/luggage van