And together this entire structure connects the F not to the F one section. So a single A subunit that binds to the outside of the C ring structure and the A subunit helps connect the F knot to the F one unit and also plays a role in proton transport. Now up to this point we basically see that the F zero region and the F one region are bound to one another at two locations by two structures. The first structure that holds the F zero to the F one is that central stock that consists of the gamma and the epsilon. So the gamma epsilon central stock connects the F zero region to the F one region. On top of that, we also have this arm on the outside composed of the single A, the two B structures and the single delta structure that hold these two units together.