[Sproket]

I did think about that but I said to myself I will remember, then someone interupted me. S h i t...
The only thing that matters is if you dont put the center piece in right then the impingment (spelling) jet wont be over the cpu core exactly. Could vary by a couple of degree.
Thats why Cather put 3 little dots on side of block to mount properly.

Most pics show it being a little to the right when you look down the center tube.