The Mobile Phone Magnetic Vent Mount works great and is easy to install.
The magnetic vent mount comes with a thin magnet that slides between your phone case and the back of the phone. So, you do need a case on your phone. Then the magnetic vent mount just slides onto one of the vents in your car. The magnet does all the work. You can use your phone in both landscape and portrait without any changes to your installation.
I have purchased three of the TechMatte® Magnetic Vent Mounts and have also purchased the extra pack of TechMatte® Replacement Magnets. I have used this with a phone with an Otter Case and a couple other cases and it works great. I did have an issue with a generic metal case blocking the magnet.