I wanted to be able to carry a couple of things along with my phone so I wouldn't have to worry about carrying my wallet everywhere. This case has a little slit that can carry a credit card, drivers license, etc. It also has a little kickstand that let's me position the phone in landscape so the kids can watch an impromptu movie, you can put on the dashboard for GPS, the list goes on and on.
You're going to be printing a total of ten pieces, two copies of the volume button and one each of all the rest. On my Up! printer is was using 0.2 mm Z, hollow fill, and normal speed (I used fine for the first couple of prints and it's overkill for this project). After you've finished printing clean up any support material and then you should be ready to assemble.