Peep Sight Hole Demension: the viewing tube diameter is 16mm, out eye diameter is 32mm Applicable Door Thickness: 18-32mm Made from brass and glass with brushed satin chrome finish, durable and solid Wide View Angle Glass Lens: 220-degree visual angel, offers a crystal clear view with an extraordinary wide angle coverage Secure Peephole Cover: increases your privacy, prevent visibility from the outside CHROME FINISH  for doors from18mm thick up to 32mm thick