This track has 34 segments and is a little less than 3 studs wide. With its deep tread, the rubber provides excellent tration. The loop must be driven with a special type of sproket wheel called a tread hub; the track requires two hubs 13 studs apart to be fully streched, as shown in figure 16-1. Tread hubs have a diameter of 3 stud, and their width is just a little bit less. They come in a variety of colors, and they use pin holes. In order to mader to make your sprocket gears rotate with an axle, you must lock them with 16-tooth gears, as shown in Figure 16-2 You'll need two 16-tooth gears per hub-one on each side-or, to save space, you can use a single gear on one side and a bush on the other.