M28 designates a series of small shunters designed by MÁVAG and built by Rába from 1955. They have two axles and were originally powered by a 130 hp Ganz diesel engine. There was a variant with mechanical power transfer and a top speed of 30 km/h that was called M28.1 by the MÁV and another one with a hydromechanical gearbox and a top speed of 50 km/h, called M28.2.
The MÁV received 24 M28.1 and ten M28.2. Around 75 more were built for private operators and called A21. They also got the nickname “Raisin”. Originally used as station pilot and for light transfer services, many are still operating in the 21st century. But today, they are only used in depots and workshops. In the meantime, many were upgraded with license-built MAN motors which deliver 200 hp.