Let me correct what I said before. I bought a ring, but it was not the proper size - so I'm using a regular metal plate (this one to be specific -
https://amzn.to/2xuZvp4 )
I've had my phone in a bumper, so the back was exposed for the whole year and the plate was mounted to the phone. Now, I got an apple leather case and the plate is between the case and the phone.
Phone holds well on the magnetic holder