The Flak 30 (Flugzeugabwehrkanone 30) and improved Flak 38 were 20 mm anti-aircraft guns used by various German forces throughout World War II. It was not only the primary German light anti-aircraft gun, but by far the most numerously produced German artillery. Rheinmetall developed the 2 cm Flak 38, which was otherwise similar to the Flak 30 but increased the rate of fire to 220 RPM and slightly lowered overall weight to 420 kg. The Flak 38 was accepted as the standard Army gun in 1939.