Sd.Kfz. 7 - Basic Sd.Kfz. 7 half-track vehicle, with open bodywork and theatre-type seating for gun crews. No armor, used as the tractor for 8.8 cm FlaK gun and 15 cm sFH 18 howitzer
Sd.Kfz. 7/1 - Sd.Kfz. 7 armed with 2 cm Flakvierling 38 L/65 quadruple anti-aircraft gun, open and armored cab variants. 750-800 produced by the end of December 1944
Sd.Kfz. 7/2 - Sd.Kfz. 7 armed with 3.7 cm FlaK 36/37 anti-aircraft gun (switched to 3.7 cm FlaK 43 in 1944), open and armored cab variants. ~1000 produced by the end of January 1945.
Flak - Flugzeugabwehrkanone (anti-aircraft gun)
3.7cm Flak 37 - Flak 36 with simplified sighting system
can be mounted on vehicles, tank & aircraft (Ju87 & Hs129B-2/R3)