The M131.1 (801) series railcars were designed for passenger transport on secondary lines. Serial production took place between 1949 and 1955, with a total of 550 units manufactured. They have a simple, low-maintenance design with a mechanical transmission and a Tatra engine. The M313.1 railcars were in service throughout Czechoslovakia until around 1980. To increase capacity, various lightweight passenger cars were attached, or Clm and CDlm series cars with a similar design were used.

The M131 model has two powered axles, a KKK slide and a Plux22 interface. Accessories included.