I did not do the installation myself, but I had a problem with the flexible hoses that went from the metal tubing to the drum itself. I think these may be the fittings and threads that you may need to know about
:
https://www.etrailer.com/Accessories...s90ff-1-5.html
You can enlarge the image and see the threads and fittings pretty good. I had to drive from Brunswick, GA to East Texas without any trailer brakes because no one had these hoses in stock. I now carry some extras.
If I'm barking up the wrong tree, just forgive and procede.