Product review (1 stars): Never again JENN AIR !
I have had to buy these knobs several times and each time they break at the sleeve insert. They are composed of cheaper plastic than that put into the cheapest plastic toy you can think of.  I am getting one more set but this time I am going to apply two or three coats of JB Weld epoxy glue around the outside perimeter to try and strengthen the cylinder wall. Plus, I will make sure we never buy another Jenn Air product of any kind.