The chassis design for the first production series was based on the "5.Serie/Z.W." design (also known as the Pz.Kpfw.III Ausf. E). The component parts of the chassis specifically designed for the first Sturmgeschütz production series was the hull armour (with drawing/part number 021St33901); hydraulic assisted steering (021St33932); driver’s seat (021St33933); brake ventilation (021St33934); track brakes (021St33937); and the final drives (021St33938 & 39).