Officially presented at the opening of FIAT's Mirafiori plant in May 1939, the AB 40 was, at the time, something of a cutting-edge vehicle. Thanks to innovative solutions such as double drive and spare wheels mounted as neutral to help get over obstacles, it was a match for any foreign rival in the same class. The AB 41 version, introduced in 1941, included several improvements, as the one to the main weapon, a 20 mm Breda model 1935 cannon.