This is the video doorbell that replaces an existing peephole and lets you see, hear, and speak to visitors from anywhere. Whenever someone knocks on the door, presses the doorbell, or triggers its motion sensors, a 1080p HD camera with night vision sends an alert and live video to an app on your smartphone, tablet, or computer. A built-in speaker then allows two-way conversations as if you were home. Can also be operated via voice commands on compatible Alexa devices. Installs easily in most standard size peepholes (1/2"-9/16"), standard thickness doors (1 1/4"-2 1/4"), and functions as a standard peephole. Removable battery pack provides several months of operation on a full charge via USB. Requires connection to your WiFi network. 4 1/2" H x 2 1/4" W x 1 1/4" D.