Lamp Holder Sockets with Photo Cell Sensors automatically turn ON Lamps at dusk or when it is dark and turn them OFF at dawn or when exposed to light. This is a 2 pack set. These instantly turn any lamp into a home security system protecting your home and family. Easy to use electric eye sensor simply screws into any light socket. Light bulbs then screw into the sensor. Bulbs to be used are standard size incandescent bulbs 60 Watts to 150 Watts Maximum suitable for a screw type socket. You may need to adjust the positioning of the sensor to get the right position to avoid other sources of light from streetlamps or other ambient light to make the lamp work as desired. It is suggested to used duct tape or other opaque tape to cover as part of the sensor to tune the sensor to work as desired for various lighting conditions. This is not for use with flourescent bulbs but only incandescent light bulbs. Also please note that this unit is designed to work with the U.S. Voltage 120V and Frequency 60 Hz of the U.S. and the socket is a screw type socket. So if you are in another country please make sure that the voltage and current frequency match the U.S. Standards.