The Reliance Controls P4121 Photo Control, Stem Mount is a thermal-type photo control with a bottom-threaded mount. With this product, you will be provided with assured dusk-to-dawn lighting control. The delay action also ensures that your light will not turn off due to car headlights. Furthermore, moisture is a total non-issue since this features a cadmium sulfide photocell and a sonic-welded polycarbonate case and lens. It can even operate in temperatures ranging from -4 degrees to 167 degrees. Since 1909, Reliance Controls Corporation has contributed more innovations than any other single manufacturer and has been awarded over 85 patents on manual transfer switches, time switches and accessories. Reliance Controls Corporation specializes in the manufacturing of a wide variety of electrical products. The primary product line consists of heavy duty time clocks and controls, generator accessories, transfer switches and transfer panels for portable generators. And after over a century of innovation, Reliance Controls Corporation has built an enviable reputation for high quality, superior engineering and exceptional customer service.