I would imagine hes looking for the bell-shaped plastic piece that goes on the end of the hinge-pin, and slides into the block screwed to the chassis.
Funny enough, It was one of those that split when I crashed mine, and is now missing. I too noticed no one had the A parts listed.
On the positive side I did manage to spend a few minutes looking for my missing dog-bone.
And then left it on the table at the track....
Which meant a 2 hour drive back to get it at 10pm.....
....silly bugger.