Harley Benton Parts Dome Speed EB Ring

Pretty good quality knobs. I suppose they aren't made of real ebony, but a plastic or resin of some sort. They look great though. The only bad thing are the two rubber rings around each knob: when I received the knobs, the rubber rings were brittle already, but they haven't broken yet. How long they'll last only time will tell.
If you're looking for a cheap alternative that looks great, go for it! They do the job just fine and look pretty good.

Very nice. However. I doubt the rubber bands will last. They are also not perfectly even all the way around. It's a set of 2 pieces. I hadn't noticed, so now I have a spare pair.