The OF191 from Alpha is an entry panel frame made of heavy gauge extruded aluminum, in a natural (clear) anodized finish. It is used with a variety of apartment entry intercom and video intercom lobby panel modules, alphabetical directory modules, as well as specialty and annunciator modules. The 19″ height on the it is ideal for mounting alongside standard 19″ high vertical mail boxes, if required. It can be used by itself, or with the matching Oh29X series flush back box/housing.