1Applicable door thickness: 35-60mm / 4-4in, suitable for wood, fiberglass or metal doors, can effectively protect your home from burglary and home invasion. 2Easy to install, the door viewer can be replaced within 5 minutes without tools, providing the highest level of protection for your safety, convenient to use. 3The 220-degree viewing angle provides the security of identifying visitors from behind the locked door, you can easily see who is standing outside, practical. 4The lens is composed of convex lens, focusing tube, concave lens, concave lens, washer, convex lens and metal frame, durable in use and has a long service life. 5Precise thread, the length can be adjusted properly, anti-twisting, anti-skid and anti-prying, effectively prevent thieves from prying and destroying door viewer. 6A sturdy viewer cover increases your safety, after cover the cover, visitors outside cannot see through the viewer into your home, protecting your safety.