These door viewers are constructed of solid brass housings, and they come in a polished brass finish. The lenses of these viewers feature a 160-degree angle of view, and it can be installed on doors from 1-3/8 inch thick to 2-1/8 inch thick, with a required 1/2 inch diameter hole for installation of viewer. These door viewers are designed to provide security when entry doors are opened for ventilation and visitors. They are ideal for day or night viewing with (adequate exterior lighting), they are easy to install and are used by many. Inside viewer covers are also available from the manufacturer (not included with this item), which are designed to prevent reversed visibility through door viewers increasing the security and privacy of your home.