The Northern Illinois indoor/outdoor LED Logo Thermometer is made from a UV resistant black ABS plastic and the glass face lens has a rubber gasket to seal the weather from the inner thermometer housing. Four LED lights controlled by a photo eye turn on automatically when it is dark to illuminate the thermometer face. Factory Calibrated to Accurately Measure Temperatures from -40 degrees Fahrenheit to 140 Degrees Fahrenheit. Artwork is digitally printed with UV inks to ensure years of fade free, vibrant colors. LED requires requires 4 D batteries (not included).