I’m not sure about the size but I know on the JJ ash catcher there is a “nipple bump” in the center that is used with a screw head from the legs ( like SJ style legs )to hold it under tension.
So I guess the answer is NO, it’s not the same.
Also.. the WSM is only a heat shield and has a water drain hole. JJ is heavier and more like a reg ash frisbee on a standard new kettle with a heavy rolled edge.
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