Welcome to Angel Electronics!
Best Mounts low voltage mounting brackets are better and easier to work with for low voltage retrofit installations. They are flexible enough to be used with walls from 1/4" to 1" thick. The bracket is its own template - simply trace a hole along the inside diameter and then cut along the outside of the line
Recessed, oval-shaped screw holes allow for final shifting and straightening of the device when installed. It even doubles as its own cut-out template! All in all, this bracket installs in less time than steel or plastic mud rings and costs less, too. Install either vertically or horizontally based on the needs of the old-work application.