Once installed, the viewer yields good results. It provides a clear, wide angle view. From the inside, viewing a person standing near the door, you can view the top of the head down to about waist level. With no one around the door, you can easily view the entire surrounding area.BUILT TO LAST AND WIDED USED - Constructed from Durable Solid Brass, leads for a very long durability and lifespan. Perfect for home, office, hotel and front doors where you need to view who is outside your door before opening, providing you extra privacy and safety. A must complement for any intercom system, security door monitor, door accessories.QUICK & SIMPLE TO INSTALL - Applicable Door Thickness 1.97 inch to 3.34 inch (50mm-85mm) thick doors, simply drill a suitably positioned diameter hole in doors 0.86 inch /22mm, insert the viewer into the hole then screw the two sides together and tighten by hand. After finishing the installation , you could see the entire outer surrounding so easily.Its material is solid brass,high quality door viewer and has a nice 220-degree visual angle. After installed it,you could see a lot of the area. It offers the highest quality security for you and your family.100% Satisfaction : Your smiling face is our pursuit. If you are not satisfied with our products, please contact us and we will give you a satisfactory answer. We provide full refund and return service within 30 days! So, trust your feelings and add it to your shopping cart as soon as possible.