Water tight covers were put around access doors, air inlets in the engine, gun mantlet, and all vents had new seals for wading. Bosch lights were fitted to fenders. Smoke candles were replaced by 90 mm NBK smoke mortars on each side of turret. Many were fitted with side skirts on hull and turret (Schürzen). Late models had a deflector ring around the commander's cupola. Some had Fliegerbeschussgeraet (machine gun mount) installed on the cupola for antiaircraft defense.
The hull escape door was eliminated.
In July 1942 the order for 1,000 was reduced to 775 as the OKH had plans for replacing the PzKpfw IIIs with Panthers. It was decided to use 165 PzKpfw III chassis to build StuG III. 100 were converted to flame-thrower versions.
The 75 mm gun's AP round weighed 15 lbs, and had a muzzle velocity of 1,263'/sec.