That grommet for the walbro carb is part number 1123 123 7500 according to DIY spare parts. Should look something like this. I just replaced a wt-215 on an 025 with one from farmertec, working ok so far. I did have to turn down the diameter of the idle screw head, it was too fat to fit in the grommet. About 1-1/4 turns out for both h/l. Came with over 2 out of the box, crazy rich.
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We stock the carbs that work with those as well as the 0603 where the low and high needles are further apart and the grommet holds the tank vent as well.
I replace it with whatever was on it. Both of those are fully adjustable. So, I'm not sure why one would be better than the other.
The majority lately have no high adjustment at all, just a reverse thread to increase the idle speed.
Not crazy about those, but they work OK until the jet stops up.
Which it will, if you only use them periodically.