Product review (5 stars): WooHoo!
Finally found the correct size knob for my Jenn Air range.  It took several tries and a call to their customer support.  Their website was no help since my range is 10yrs old.  Apparently there are serial numbers etc on metal tags on the top part of the range behind the electronic controls.  Once I had them, the customer service rep was able to give me the correct part number.  Altho they did sell them on their site they were considerably more expensive so I found them here on Amazon.  I'm  cooking with gas again!