Eliminate dangerous glare from the vehicles traveling behind you with an Gentex rearview mirror. It detects glare and automatically dims to preserve driver vision and make nighttime driving safer. The brighter the glare, the darker the mirror becomes. This mirror also has three HomeLink buttons. About HomeLink :: activates RF-controlled garage door openers :: operates RF-controlled lighting, gates, entry door locks, and more :: can be easily programmed to meet your needs for security, efficiency, and convenience. Compass readout also ensure that while you are driving safer you are also driving smarter.