Yesterday, someone having a go on my bike came off and the mirror got damaged, the head was missing. To took a while to find it deep in the mud but the glass was not broken.
Later at home, I cleaned it and was able to re-insert the brass serrated threaded part and then re-assemble. It's almost as good as new, I doubt any other than the Mirrycle would be so engineered to enable such a repair.
I have a Zefal on my Birdy, always having to adjust it. Nice view from it though, preferable to the Mirrycle but not good enough to replace it.