Did you figure out which one to use? I was installing URLO grips and came across the same. Guessing it's the largest of the three adapters? Tips for making it twist smoothly? it looks like the adapter shouldn't be pushed all the way onto the teeth - needs a gap for the little ridge in the throttle assembly?Maybe Im missing something...
The adapter that looks most like the stock piece has squared off cut outs vs the triangle edges of grip.
For those of you using Rizoma grips on a Scrambler, which adapter did you use?