I am learning that the BMW "auto-dimming" (a.k.a electro chromic) mirrors are protected by one or more patents!! That is why one cannot get these as aftermarket (or in blue). These mirrors have an dealer list price in excess of $300/ea!!!

Here's a little info on how these electro-chromic mirrors work:

Working operation of Electro chromatic mirrors:

This auto dimming mirror is typically installed on higher end vehicles. It consists of two lenses that sandwich an electro chromic (electronic color changing) gel. The inside sides of the lenses are coated with a transparent conductive layer coating and the deepest lens has a reflective coating.

This gel, when charged with electricity darkens, then clear once the glare is no longer detected. The mirror uses a forward sensor which measures the outside ambient light, and a rearward sensor to look for glare. When dark enough, it sends current to the electrostatic gel, darkening it a rate which is related to the level of ambient darkness and rearward glare. When the outside ambient light increases, the current decreases, until the gel is clear again at daylight light levels.

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PAX5
BMW CCA #20645