The cam-jam Quattro post clamp is 2”. The half shells change that to the size of the outer post of the Tiffen ULTRA 1&2. And the ring goes to the inner post which is smaller and gives it the same diameter as the outer post. So the post clamp with the half shells installed will fit. It has elevated edges, so it follows the cam-jam Quattro automatically when you move it up or down the post.