This is an auto mount for a Galaxy S3 or S5 WITH a hard cover. There is a little space given on the left and right so if you have a large case it should be fine. Without a cover it might slide around a bit but it won't fall out. Its designed to have the S3 sit in landscape mode. Might make a portrait one later.
Unfortunately the left bracket is close to the volume button so it may interfere with the use of that. I'm too lazy to adjust it, but maybe later I will.
Oh it will also work as a phone stand as well if you don't feel like putting it in your car.
UPDATE(3/4/14):DON'T USE PLA! I didn't put much thought into it at the time. It worked and fit great until i turned the heater on last night.... Bad idea... after about a half hour the vent clips spread open and it dropped out. SOOOO in conclusion, use ABS or something heat resistant
I used PLA, might have to print it in ABS later since its going to be in the car it might melt on a summer day.
The clips you should probably print with Support... clean up is a pain but it works out nicely.
The phone holder itself needs no support, I seemed to have worked out the angles correctly.
Obviously you need two