3.7 Cm Pak 36
The Pak 36 (Panzerabwehrkanone 36) was a German anti-tank gun that fired a 3.7 cm calibre shell. It was the main anti-tank weapon of Wehrmacht infantry units until 1942. It was followed in this role by 5 cm Pak 38 gun.
Read more about 3.7 Cm Pak 36: History, 37mm Pak 36 L/45 Ammunition, Variants