I took some set screws from my stock Optima joints, and they screwed into the chrome Duratrax units just as nice as can be. And since I have about 8 spare joints--some rather worn--I took one of the Duratrax screws and inserted it in one black joint, and it again bound up. It didn't get any easier as I continued screwing it in, and I basically ruined the old stock joint by stripping it out.
This seems really dumb to me. 2 sets of 2 joints and *none* of the included set screws work!
![Mad :x](./images/smilies/icon_mad.gif)