Yesterday i checked the rods of my thermoquad strip kit and I found something odd.

If i get it right, the rods consist of three parts: the upper part which is of the same diameter, the middle part that narrows downwards and the lower part that is of the same diameter again.

when comparing the different rods of the strip kit side to side, the middle, narrowing part starts in different locations (lengths) of the rod (hope you understand what i mean).

Am i correct that it is the middle part that is responsible for part throttle mixture?

If so, then wouldnt the rod tree have to be adjusted to the individual rod, so that the beginning of the narrowing part sits in the right spot of the jet?

Am i correct or do i get something wrong?

just trying to understand how this stuff works.