This unit is made from 14-Gauge steel and finished with an outdoor polyester powder-coat with UV inhibitor. Knockouts indicate where to drill holes for surface mounting. Includes a Aiphone LEM-1DL Call Master Station cutout on face plate, .5" Deep back box, with removable back mounting plate for a low profile footprint, with hidden mounting hardware. Designed to be used in tandem with single gang electrical boxes, for devices that are more than .5" Deep.