The front and both ends of the box are trimmed but the back is left flat for flush mounting to your wall. Our Direct Mount size boxes are 7.25 wide and 8 high and the trim adds 5/8 to the overall width and 1.25" to the length. These boxes mount directly to your wall by drilling through the backside of the box and using lag bolts & washers (must be purchased separately) to secure to wall studs inside your wall. The Lancaster window box also comes in two larger sizes. We offer a Standard Size (8-3/4W x 8H + Trim) and an Extra Large Size (10-1/2W x 10-1/2H + Trim).