I recently moved my URX 3.1 handguards to a different upper, so I just went ahead and used a new barrel nut. But this one is in good condition, so hopefully it may be of some use to someone. I use a different wrench than the KAC wrench. This one fits completely around the nut, not just 180 degrees like the KAC version.
As you can see from the photos, the threads look good and the lugs are not rounded or beat up.
This is the 11-notch version that is compatible with the URX II, III, and 3.1.
Asking $15 shipped. Email for fastest response and reply to this thread.