This is the easiest to install motion sensor switch. Simply unscrew existing light bulb, screw the sensor in position, and screw the light bulb into it. Automatically turns the light bulb on when motion is sensed and turns it off 4 minutes after motion stops. Perfect for closets, basements, garages, etc. (for indoor use only). Measures 3" in diameter and 4" long. The motion sensor switch can be used with 25W to 100W bulbs (not included).