In an effort to save both weight and materials, the Soviets switched from the the earlier style of tracks which had guide teeth on each link, (the ATL-14), to the later with guide teeth on every other link, (the ATL-54). Check photo references if you are building a specific vehicle to see which ones to use, although I don't know how commonly the later type were used. I've only seen a few photo so far of the later type on Battle of Berlin JS-2s, most photos seem to show the early-type tracks. One photo even shows a mix of both.