Intermatic K4121C 120-Volt Stem Mount Thermal Photocontrol A stem-mount thermal photocontrol for smart and efficient dusk-to-dawn ON/OFF control of outdoor lighting Delay feature prevents unwanted OFF switching of lights due to passing car headlights or lightning Features a light level slide adjustment to accommodate various light levels Installs on standard outdoor light fixtures and electrical boxes and commonly used for exterior lighting, street lighting, parking lot, pedestrian pathway and landscape lighting 1/2" - 14 NPSM threaded stem with locking nut and washer gasket