Scott, I suspect it's a little over one inch thick. I has a 264FS and bought a mirror from overton's but it won't fit. My taylormade windshield is about 1 1/4 thick, but it also has a rounded edge, which is another problem.
I'm researching mirrors now and think I'm going to try another one, but am trying to make sure. I reached out to taylormade but they couldn't help.
I'm waiting for a reply from the mirror company now.
Peter