pwk needle jet

[a.lo]

this part is a fixed size on these carbs and all adjustments are made with different needles, and is held in place by the atomiser which is also a single specification. my question is what difference does the length make to the jetting as a replcement i have is taller i.e extends further into the venturi? the carb is a oko version or does this part vary between other versions i.e BGM, Koso. i seem to remember this part varies between 2 or 4 stroke carbs but cannot find any info? any ideas anyone please?