Eliminate dangerous glare from the vehicles traveling behind you with a Gentex Automatic Dimming Rear View Mirror. The mirror detects glare and automatically dims to preserve driver vision and make night time driving safer. The brighter the glare, the darker the mirror becomes. Gentex Automatic dimming mirrors are based on the science of electrochromics, which is the process of reversibly darkening materials by applying electricity. During night time 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.