Miss coupling ...

Several weeks ago,I bought two step motors and two couplings but seem that I bought the wrong size.It's hole is 1/4" which should enough for two sides of the rotor and other side is bigger than 1/4".

So,I think I'll go to change it.Hope that the store that I buy will compromise me to change.

Hole of the coupling is not equal.I want both side is equal to 1/4"

This is the cheap couplings.It's only 40 bth per each.

Let see I can change it or not ?