AA ammo

AA ammo comes in three types: Firstly there is the 20mm round used by the: Flakpanzer IV "Wirbelwind", FLAK-38, Sd.Kfz. 251/17, Autoblinda 41, Sd.Kfz. 7/1, Sd.Kfz. 222 and the Sd.Kfz. 232. The next size up is the 37mm round which is used by the:61k 37mm AA and the ZSU 37. The last of the AA rounds is the 40mm which is used only in the American M19 "Duster" AAA