Product review (2 stars): breaks easily and frequently.
I have 5 of these on my Samsung range, which is about 2 years old.  Three of the knobs have broken in the time, just in normal usage.  There is a small plastic ring inside the knob that breaks, making the knob itself useless.  Samsung ought to be able to replace that plastic ring at no cost to consumers.

4 out of 5 have broken now.  I glued 2 of them back but I am still one short of a full set.  Too bad.  It's a good range otherwise.