Product review (1 stars): Beware, these knobs may not fit your stove top
I had the same experience as the previous reviewer.  In my quest to replace the knobs on my Schott Ceran glass cooktop (a Whirlpool product), I found these knobs that looked like they matched exactly to my original knobs.  Not only did they look the same, have the same specs, but also matched the product number on the bottom, KIP 5075.  I received the knobs pretty quickly, but immediately discovered they didn't fit.  They had a different insert configuration.  Unlike the previous reviewer, I haven't been able to pry that piece out of the hole without cracking the cheap plastic casing.  These knobs are very deceiving so be careful to make sure your insert is configured the same before you order.  Don't just depend on the product number.