Product review (1 stars): Did not work on 20 year old Jenn-Air stovetop
I had three problems with this product which led me to just throw them in the trash.  1. On my stove, you have to push the knob down before you can turn it and these knobs did not allow that, 2. There was no way to make the knob line up vertically, it would have been at a 45 deg angle which would have looked funny, 3. They are really junky looking compared to the original knobs.

But they were cheap enough so I figured it was a worthwhile experiment.  I'm sure there's a bunch of stoves out there they work just fine on.  There's nothing fundamentally wrong with these knobs, they just didn't work on my particular stove.

After deciding there was no way to make them work without making significant mods and they would have looked worse than the crusty old one anyway, I just threw them in the trash which I think is reasonable criteria to give a one-star rating.