? Thanks…
The axle has to have somewhere to screw into, that’s where.
Thanks - sorry for the daft question.
I was comparing it to the AC and noticed the AC did not have it (i thought it was for some kind of finger spin/grind thingy!?). I know nothing about grinds etc and am not even sure what and IGR is! Time to learn methinks!
It is actually IRG not IGR. It stands for Inner rim grind. It is the little rim towards the outside of the yoyo, where you put your thumb to grind. And no problem, you can’t learn without asking. 
IRG = Inner Ring Grinds
IGR = Inner Grind Ring
The IGR us where you do the IRGs.
Thanks for the help guys.
Now i am sure i will be going for a first run foxy moss AC as my first clyw yoyo (and also be looking at some grind tricks!).