Automatic Dimming Mirror Gentex Corporation is the world's leading manufacturer of automatic-dimming rearview mirrors. Gentex automatic dimming mirrors are based on the science of electrochromics, which is the process of reversibly darkening materials by applying electricity. During nighttime driving, the mirrors use a combination of sophisticated sensors and electronic circuitry to detect glare from rearward approaching vehicles and darken accordingly to eliminate the glare and preserve driver vision. They are popular, active crash-avoidance safety feature making nightime driving safer for vehicles throughout the world. PathPointTM Compass System The mirror's compass and outside temperature displays are features of the PathPointTM Compass System developed by Johnson Controls, a Johnson Controls Company. The compass is a self-calibrating flux gate compass that eliminates manual calibration by the factory, dealer or customer. It detects and compensates for magnetic anomalies caused by bridges, subways and large steel structures. It also compensates for actual changes in vehicle magnetics. Calibration data is stored in memory, which eliminates any requirement for recalibration after losing battery power. The electronic compass shows the direction you are heading in an easy to read digital display located above the mirror. The compass is an extremely accurate computer that displays vehicle headings of N, NW, W, SW, S, SE, E and NE. Outside Temperature Display The outside temperature display provides you with a digital temperature reading. When the temperature is at or below 37 degrees the display will indicate "ICE" for a period of one minute. This feature cautions you to anticipate road-icing conditions. This is a complets kit that includes the mirror, wiring harness, temperature sensor and complete installation and operating instructions. We include a FREE Gentex wire cover to make fo a neater installation.