Review on 🚪 Premium Satin Nickel Door Viewer: TOGU TG3828YG-SN UL Listed 220-degree Brass Viewer with Privacy Cover - Fits 1-3/5" to 2-1/6" Doors by John Koch

The required opening in your door is large enough. The advantage is that it collects and transmits light very well. The glass optics make it very visible (unlike cheap eyes with plastic lenses). The lens is 0.675 inch (17 mm) in diameter. On the inside is a hinged cover that blocks the viewer. Installation: I used a 1-1/8" Forstner bit. A 1-1/8" hole saw will also work. The 1.125" (1-1/8") diameter drill bit gives you little room to install a 1.10" diameter shaft. It's easier to install a 1.125" diameter hole than finding a 28mm (1.10") drill bit. If you want a really tight fit you can buy a 28mm bit (these are available online) Looks and feels high quality This is heavy Made in China.