Product review (3 stars): Get 3/8 OD sleeves.
These work for my Jenn Air JEC8430ADS.

Like another similar product review, I bought some 3/8" OD nylon compression sleeves (Everbilt A-101) at an orange home improvement store (3x 3pack for $6) to put on the ends to prevent future failure. I heated 2 in a bowl of water in the microwave to soften, then put the thin side up on a hard counter and pushed the knob against it at an angle, rocking side to side, while turning the knob vertical to get the sleeves on. And then I used an adjustable wrench and screwdriver to slide the first one on to make room for the second.