Good, but read the application notes well. - ADE Advanced Optics RD3-009-2 Red Dot Sights

5 stars, but with a caveat... This product seems to be well-constructed, and the glass and dot are good, especially for the price. However, it does not fit my RMR slide cut-out, nor does the ade adapter fit my slide. This may well have been my fault. Perhaps I misunderstood the advertisement. Obviously, the picatinny clamp allows this optic to be used on about any rifle rail, but the optic is too long to fit into my cut-out. I have concluded that for pistol use, it is designed to use only with the rear sight dovetail adapter. No problem for me, for I have other handguns that I can use it on.