If the knobs on your Becker CDR-220 have become sticky this is an inexpensive way to replace them. Mine became so malleable I didn't even want to try any of the remedies that people suggest. Replacements were definitely in order in my case. Factory originals can be purchased from Becker for $40, if you don't mind spending crazy money for a couple of pieces of plastic.

They are not exact copies of the original knobs. I tried duplicating them but the shortcomings of 3D printing got in the way. I made a small compromise so that the printed result wouldn't require any further manipulation. They are close enough that no one will notice that they're not original.

They may fit other Becker radios.