Yep you got it
Its a steel ball that has a hole down the middle of it a self tapper or a fine thread bolt is fitted through the hole and screws or bolts to your throttle arm on your carby your throttle linkage has the ball cup end on it and is placed over the ball and pushed on[sm=49_49.gif].
To remove it you have to pull the ballcup off the ball.
You can actually buy a tool to do this or you can lever the ballcup off the ball with a screw driver or fine pointy nose pliers.
Hope this helps