Door Knocker Collection Door Viewer for 2.25 Inch to 3.25 Inch Thick Doors Designed with both safety and functionality in mind, Baldwin"s Observe-O-Scopes give you the advantage of knowing who is at your door before you have to open it. Each viewer features specially constructed exterior glass to prevent scratching, a 180 degree field of vision, an interior shutter and easy installation (simply drill a hole in the door and tighten the viewer into place). In all, Baldwin Observe-o-scopes are a simple and effective way to increase your home security. Features: Adjustable for Door Thickness from 2.25" to 3.25" (33 - 57mm) 0.5" (13mm) Diameter Quality Lens Exterior Lens Constructed of Scientific Glass to Prohibit Scratching 180 Degree Field of View Includes Brass Shutter Easy Installation: Simply Drill a 0.5" Hole Through the Door, Insert Viewer and Tighten to Fit There are brand names, and then there is Baldwin. Constantly building and re-building upon a time tested legacy of superior design, craftsmanship, functionality and innovation, Baldwin Hardware has delivered modern luxury to discriminating homeowners, architects and designers since 1946. From being the first to forge solid brass door hardware to setting precedence for Lifetime Finishes, Baldwin has been and always will be synonymous with revolutionary technology and unsurpassed quality. Aspire to make your home much more than mere shelter, and relax in the assurance that function and elegance can finally flourish within the same line of fine products—Baldwin can show you how.