[DisillusionedPrepper]

Yeah... The Pict. I posted is a 26mm CVK or Vacuum type carb.
That's best for a lightly modified 150cc or highly modified 125cc, and still gets decent fuel mileage.

If you're going to do all your mods at once, and try to save a few bucks then I would go with the 28mm Flatslide carb.
If you're going to go in stages then the 26mm CVK is good enough to get you thru the entire process, and you can add the flatslide as a cherry on top once your finished modding.

I have a box full of carbs that I used at different times, and different stages of builds.
It just happens. You'll end up with a few boxes of GOOD parts as you modify these engines. When you have someone build your engine, get ALL the original parts back.
Besides everything else... It never hurts to have a spare something laying around for those "suprise" moments when the bike just won't run right.