My personal experience with the Wondersight is not so good. I bought a very nice 1920s-era M&P a few months ago, and it had a Wondersight mounted on it. At my first range trip, it became obvious that the sight could not be lowered enough to zero at 25 yards with the existing front sight, and it was hitting, as I remember, about 6"-7" high. No question that the sight picture is vastly better than the fixed sights, but one would have to adopt a different sight picture to compensate for the amount it shoots high. I took the Wondersight off and replaced the bug screw. It was not too easy to find one of those, but one of the members here helped me out by selling me one. When I removed it, I noted there was a small amount of frame scratching under the Wondersight, not bad, but it does bother me. Just be aware of what to expect if you mount one - and make sure you put the bug screw someplace safe.