Product review (3 stars): Coupling has a metal center
Note that the main picture is not accurate.  This coupling has a METAL center rather than plastic/nylon center.

Many websites recommend that you use a coupling with a plastic/nylon center.  If you use the metal one, you run the risk of the metal from the coupling stripping the post of your motor.  It is much better to keep the post of your motor in tact, and let the plastic/nylon center of this coupling take the wear and tear.