Review on High-Quality Coarse Coupling Nuts (3/8-16), Pack of 8 - Hard-to-Find Fastener 014973322144 by Cody Clark

I just received them and have modeled what I wanted to do. I ordered 3/8"-16 roughly down the line and expected everything to fit. I grab the screw and it won't thread. It's best I do 1/8 turn before it connects as had it cross threads. After confirming that everything looks right and my orders are correct, I get other 3/8"-16 thread hardware and it all comes out the same. As a final sanity check, I decided to just run it and see what happens. After severe twisting with pliers, the thread will run in normally. Constant grinding and significant resistance. I get bigger chips than cutting holes in the open side of the nut. It's a decent deal if you have to go through faucets otherwise I'd be wary.