Bought a pair at Meripäivät some time ago, now I can rotate them with my off-hand splendidly, and somewhat with my right hand, too, widdershins and in reverse. It's in the thumb.

But let me tell you, these things are NOT therapeutic. Damn, I don't know what would happen if I'd do this for too long, but it would be painful.

They make a pretty sound, though. I wonder what it looks like inside.