According to the company, these are less aluminum bumpers, and more TPU cases with aluminum accents:
Excellent questions. First off, this is not (nor any one of our cases) are all aluminum. The aluminum is minor, more for accent, and is inlayed into a recessed area of the TPU, via a special overmolding process. The overall look is that of aluminum, but without the hassle of screws. The iPhone squeezes in to the case, as the TPU part is slightly expandable, yet snaps back to assure a tight hug. The aluminium is very thin, and of course we took into consideration signal, gps, etc.. This does not affect it one bit. We've tested it in field test mode over several weeks in a variety of weak areas and a few countries overseas.