And this is what we focus on in the previous lecture. In this lecture, we're going to focus on the F zero region. Now remember that the F zero region actually consists of two types of polypeptide subunits. We have the C subunit and we have the A subunit. Now, we only have a single A subunit. But for the C subunits we have anywhere from ten to 14 C subunits that aggregate together to form something called the C ring.