All OEM Mikuni jets from the Japanese factory are flow rated and every individual Mikuni Jet size item is absolutely identical.
For years we’ve issued advice for customers to identify genuine Mikuni jets by the small box in the corner of a larger box stamped on every jet but unfortunately fake Mikuni jet copies are now appearing with this stamping on them also. Bearing this in mind your only guarantee of actually purchasing genuine Mikuni jets is determined by the integrity of the supplier.
Trying to make Mikuni jet adjustments and correctly tune an engine using inaccurately sized fake copy jets quickly turns into a nightmare and can easily cause expensive engine damage. Only ever use genuine OEM Mikuni jets and NEVER drill them.