I've never seen ST needles with different thread pitch and diameter. Maybe Randy means different lengths?
I think there are 5 different length spray bars and some of the needles can cross over to be used in a different spray bar but they don't all interchange.
MM
Yes I said at least 4 different ones, Your right as there maybe 5 or 6, they are the same threads, but here are some reasons they do not work, some are very long, some are very short, there is a very short one with a longer thinner taper, and other have slightly different tapers, there is even ST needles out there that are slightly smaller diameter
Some of the long thin tapers from the 11 or 15 will not work in other spraybars, vise=versa for the longer ones
Randy