I bought this because I cover my 5s 1. wanted to get clean even in my Bugatti leather case and 2 in my mount in the car also wanted to get clean. What also works well.
One star deduction there because the description is "... strong design ..." and it's not.
To let off a few cm height fall the iPhone holds out the envelope. But by their lack of rigidity or strength it would give the impact energy during a fall in the scope of the 5s on and Verforungen are as likely.