On this viewer, the plate rotates freely and has a quality feel to it, this privacy cover is great for stopping those with reverse peepholes from spying on you. Maybe you initially was going to buy the cheaper, smaller version but you will be glad to spend the extra for this onePerfect peephole for home, office, hotel and front door where you need to see, monitor, spy and peeking who is outside your door when the doorbell rings before opening, providing you extra privacy and safety. A must complement for any intercom system, security door monitor, door accessories.Its material is solid brass,high quality door viewer and has a nice 220-degree visual angle. After installed it, you can view a person who standing outside from the top of the head to the feet, and you can easily view the entire surrounding area.It offers the highest quality security for you and your family.The required hole in your door is 1.1" / 28 mm, it is quite large. But the payoff is that it is very good at gathering and transmitting light. It is very clear through the glass optics (unlike cheap peepholes with plastic lenses). The lens is 0.675" (17mm) in diameter. Because the lenses are large, the image shows up nice and clear.This suitable for 1.65" to 2.16" ( 42mm - 55mm) thickness doors.Insert the viewer into the hole then screw the two sides together and tighten by hand. The viewing tube is somewhat larger than many other standard peephole viewer, offering a better field of view. You can apply a thin coat of silicon sealant to the inside and outside flanges before installing the unit, to help keep moisture out.