The M4 is a narrow-gauge diesel railcar built by FIAT for the Ferrovie Calabro Lucane. It was based on the ALn 663, but was shorter and had its Iveco engines limited to 250 hp. Each engine powered both axles of a bogie due to the lower axle load. There was the basic M4.300 variant with two engines and the M4.350 where only one bogie of each car was powered. The 350 variant was usually used in pairs. Only two units could work in multiple, so working with three or four motor cars needed an additional driver.

The FCL received 15 M4.300 and twelve M4.350. Additionally, some non-powered trailers were built. For the rack section between Catanzaro Città and Catanzaro Lido, ten M4.350c were built which are based on the 300 variant, but have an additional Strub rack drive on each bogie. Due to the lack of rack locomotives, they are also being used for work trains. After the FCL was split into the Ferrovie Appulo Lucane (FAL) and the Ferrovie della Calabria (FC), the FC received eight of the new variant M4.400.