The 2.0cm Flak (Flugzeugabwehrkanone) was introduced in 1940.   It was a good reliable gun with a high rate of fire, but only effective to an altitude of about 6000ft..   It could fire HE or AP shells and was frequently used against ground targets.      It was either towed on a small, two-wheeled trailer (Accessory Pak A28) or mounted on a variety of tracked, half-tracked or wheeled vehicles.