First the good: It's a nicely solid piece of machined aluminum. Anodization overall is consistent and bright. In short the appearance is great.
However, it's a loose fit on the knob. It will leap off unless you secure it with some tape or adhesive. It's loose enough you can't even open or close the vent with it on. It will just rotate freely. If it had a little light duty adhesive strip like the vent surrounds did, it would be perfect. As it is, I really won't be able to use them until I can find a way to keep them from falling off.