Hello! All of the CNW coupler nuts have electroplated zinc finish which does not provide required corrosion protection for exterior applications. You would need to source a coupler nut that was hot-dip galvanized and then over-tapped for fitting onto hot-dip galvanized threaded rod.
The CNW5/8 has 11 threads per inch. Thank you!
The coupler nut is 3.5" high.