I read all the post on this thread, about the different types (brand names) of glue to re-attach the rear-view mirror on the X type. Mine fell off but after reading these posts I was hesitant in using either glue type mentioned as none explained a permanent fix (fell off after a couple days/weeks/months). I called Safelite and other glass replacement shops and none would touch it. So, I called a local private owned windshield replacement shop, and he did the job. He used (Loctite) polyurethane (black) to re-attach the mirror button and said that is what the auto manufacturers use to install windshields. I know this is so on the X-type cause when my mirror fell off, there was a leftover polyurethane ring on the glass which he removed and cleaned the glass before re-attaching the button. And I've never seen a windshield come loose without using a windshield removal tool. After gluing the button to the windshield, he taped it in place, and I have to wait 2 days for it to fully cure - then I can attach the rear-view mirror. It's been just one day, and I will follow up in a couple days, after I re-attach the mirror. Fingers crossed but I have faith in the man's knowledge.