Product review (3 stars): Warning: these have metal inserts which don't fit without filling
The main picture of this coupler shows them to be all plastic but I received ones with the metal inserts which I didn't want.  Tapping one of the new ones on it broke because it was WAY too tight.  I had to spend about 30 minutes filling the other one down just to make it fit properly.  Bring back the all plastic ones!!! The metal insert ones are junk. In the picture the new one is in the center and the one broken in half was the original all plastic one that lasted 12-13 years.