StuG III Ausf. B: (Sd.Kfz 142; June 1940–May 1941, 300 produced by Alkett) Modified 7./ZW chassis (Panzer III Ausf. H), widened tracks (380 mm). Two Rubber tires on each roadwheel were accordingly widened from 520 × 79 mm to 520 × 95 mm each. Both types of roadwheel were interchangeable. The troublesome 10-speed transmission was changed to a 6-speed one. The forwardmost return rollers were re-positioned further forward, reducing the vertical movements of the tracks before they were fed to the forward drive sprocket, and so reduced the chance of tracks being thrown. In the middle of production of the Ausf. B model, the original drive sprocket with eight round holes was changed to a new cast drive sprocket with six pie slice-shaped slots. This new drive wheel could take either 380 mm tracks or 360 mm wide tracks. 380 mm tracks were not exclusive to new drive wheels, as spacer rings could be added to the older sprockets.