Secondary roles are assigned to both the C1 and the C3 in the Cyclic Tag System; nevertheless these roles are important ones. Single C3's alternate with C1 pairs when the transmission of a flotilla of EBars is required, albeit with attrition.
Figure 7 shows the four C3-EBar collisions. Two dissipate into B groupings; one a tetrad, the other a common artifact in E collisions. There is also a double exchange, flipping EBar for F alongside flipping C3 for C2. The fourth has a critical place in the Cyclic Tag System, because it alternates the C1 pair with C3's to create a semipermeable membrane which lets a third of the Ebar's through.