Alan--why not get Volvo's self-dimming mirror? That way you won't have a hole in the overhead assembly where the mounting bracket was. It was made for the 70 series, but fits perfectly (including color) on all the 850's. It wasn't a really popular item with Volvo, and the last time I checked the price on it, it was in the thirty to forty dollar range. Hooking it up is not a biggy, though you have to know where to hook the blue wire (it comes with a brown, black and blue) for the mirror to turn off when you back up. When you're in reverse your backup lights will make the mirror dim. I don't know if your Gentex has that option on it or not. If you decide to get it, a cheap Volvo dealer to order it from is Volvo Houston, 1-800-468-0041. If you have problems, let me know and I will tell you where to connect the blue wire, as well as the other two. It's not shown in the instructions that come with the mirror. Contact me at my email address: rtparr@frisurf.no Dick