The unit has a flange that grips the grinding wheel.
It also serves to reduce the 1" hole in the wheel to
the size of the spindle. Much more accurate than those
little plastic rings they give you.

The flange has a "circular T-slot" so you can position
weights (= bolt, nut wshers)around the circumfernce,
much like balancing a car or motorcycle wheel.

It is kind of spendy, but it does work very well.

I think I had to machine 0.065" off the end of the flange
to get it to work with my grinder.

On my big pedastal grinder, I rotate the wheel and dress
to get it "good enough". On that grinder I don't do any
kind of precision work--just ginding off burrs and using
a wire wheel.

JLD