The Extreme Duty Fixed Sight will convert you K, L, or N-Frame Smith & Wesson with adjustable sights to a fixed sight tactical revolver. The dovetail front sight requires machining a dovetail in the front sight base. Rear Sight installs directly to New Style Revolvers. Old Style Revolvers require drilling and tapping of the top strap. Installation of the dovetail front sight allows you to zero your revolver precisely for windage and elevation.