This is a replacement rear sight for those Smith & Wesson K ,L, N and X-frame revolvers that were factory drilled and tapped for a scope base. It is fully adjustable for windage and elevation with hardened "click" screws. Features: Works with the factory front sight. Fits the existing slot without milling work. Machined from solid steel using state-of-the-art cnc milling. Allen wrench and adjustment screw driver included in the package. Mfg: L.P.A. Sights