We have the C unit, the C subunit as well as the A subunits. And together the C and the A subunit basically interact to form this proton channel that allows the movement of those protons across the membrane of the of the mitochondria, the inner membrane of the mitochondria. So the F knot region consists of ten to 14 C subunits. So in this particular case I've drawn ten. So we have 1234-5678, 910 of these orange structures and these ten C units basically organize themselves to form this ring structure which acts as a channel to allow the movement of those protons. So the ten to 14 C subunits organized into a ring structure that act as a proton channel.