John, I've only owned 6 4200's, all 2.5-10's, so I can't speak for the rest of the line. If there's a difference between them (mine that is) I haven't seen it. I will say that the 4200's seem very slightly better in the optics department, but they all track and hold zero damn near perfect, best I can tell anyway. More than I can say about the brand they replaced. As far as I know, they are still made by Light Optical Works as they were when they were first introduced (as the 4000 series makered Bausch & Lomb) in the mid 90's. I have heard of some dud 6500's early on, but I don't have any experience with them.
