The magnet is nice and strong, but the weight of the phone combined with normal road vibration cause the assembly to fall.

For my Large GMC truck I put this on the vent with my iPhone 6 7 and 7 plus and all just fell out and off the vent wouldn't hold the weight period to bad too because the magnet works

The only problem I see is the weight of the part that goes in the vent

I dislike that the magnet, it adds overall weight to your phone and may interfere with your case.

and it also cannot support the weight of my iPhone 6s, just a total flop

Mine is already broken I like to