Mounts that have any type of sliding action against the rail WILL remove anodizing and therefore mar your rail. To the poster that said it was cosmetic only: it’s not. Companies like Nightforce specifically suggest avoiding the use of friction-based mounts (namely LaRue Tactical ), as the rail becomes permanently deformed (if only microscopically) and the mount must be re-adjusted over time. I’m sure some of the hardcore LaRue Tactical fans, as well as the function-first types will say it’s BS and that it doesn’t matter. A quick review of basic engineering will prove this is not only 100% correct, but it’s expected from mounts of this design. In regards to it not mattering, that’s subjective. If you safe queen your rifles or have precision rigs, then it matters just as much as the ammo that you buy for your guns. If you’re a carbine-course regular who will shoot out their barrel in just a few years, then you won’t notice. Either way, it does happen and it is a factor to some people.