After the Germans had lost air superiority, the interest in self-propelled anti-aircraft guns grew stronger. In early 1944 the Flakpanzer IV family was born with the Möbelwagen. This was a Panzer IV chassis equiped with a 37 mm Flak 43 covered with four shields which could fold open. Later, a second and newer Flakpanzer design was presented, the Flakpanzer IV Wirbelwind. The Wirbelwind was a Panzer IV chassis with a diamond-shaped open-topped turret that had an armour thickness of 10 mm. It contained a 2 cm Flakvierling 38, with a rate of fire of 800 rounds per minute. Although it was built to be used against aircraft, the 2 cm Flakvierling 38 was also effective against lightly armoured vehicles and personnel. Around 80 vehicles were built and the design was later replaced by the stronger Ostwind.