This is a number 3 thread which has a 3/32" diameter.
This has a flat on the needle tip section.

There is another Fox needle that looks the same but has a taper rather than a flat, The needle with a taper normally fits the spray bar with one hole.

This needle with the flat used a spray bar with 2 holes and does not work with the single hole spray bar. We found the tapered needle will work fine with the 2 hole spray bar. You must be sure the holes in the spray bar are horizontal, pointing front and back.