High QualityMade of high quality copper with plating process, corrosion resistant, more solid and durable. Adopts high-tech optical glass lens for clearer vision. 220 Degree220 degree beautiful viewing angle ensures the security of identifying visitors behind a locked door. The lens will protect your home from burglary and home invasion. Back CoverThe viewer has a 1.5mm thick cover, cover the lenses by manually rotating it to protect your privacy. Simple installationSuitable for doors 36mm-60mm thick, tube diameter about 22mm: just drill a hole 22mm-25mm in diameter , insert the viewer into the hole, screw the two sides together and tighten by hand. without tools required. Widely UseDelicate processing, suitable for doors, wooden doors, iron doors, bedroom doors.