I have a jet black 7. I typically go caseless but stick one of those thin metal discs to the back of my iPhone so I can use a magnetic mount in the car and at work. I stuck one on the back of my iPhone yesterday and allowed it some time (ie, overnight) to "cure." Stuck it on a magnetic mount I have setup at work and when I pulled the iPhone off the mount, the disc came right off and just stayed on the magnet. The back of the 7 didn't even show any residual adhesive stuck to it. It just looked like I had never stuck anything on it. I'm guessing the polished aluminum prevents these adhesives from curing properly? Not sure, didn't have this issue with my previous 6s. The other possibility is that the adhesive on the back of this particular disc is of lesser quality. I don't believe it's the 3M adhesive you find in higher quality (and higher priced) mounting discs. This was a cheap disc/magnet mounting system.