I've added a new version that supports M2 screw and nut instead, they are called _m2 at the end. Enjoy.
Insulation track joiner G scale (LGB) for code 250 rails. I haven't tested them yet since I only possess code 330 rails, but once I get some positive feedback I will remove the "work in progress"
M2.5 screws will fit this one also and apparently also 3-48 x 1/2 inch slotted pan head screws and nuts will also work as reported by rroscher.
I also added a piece of Code 250 track for testing, but this can of course also be printed.