Dusk to Dawn Sensor; With a built-in light sensor; the B11 light bulb can automatically turn on at night and turn off during the day by detecting sunlight exclusively; rather than other light sources Easy Installation; Simply screw the sensor LED bulb into an E12 socket and tighten it securely - no complicated installation procedures required The sensor LED bulb is able to function seamlessly in lighting fixtures that mustn't obstruct the light Package Content; 4 bulbs per box