Williams Fire Sight WGRS Ghost Ring Aperture sights utilize dovetail or existing screws on top of the receiver for installation. They are made from an aluminum alloy that is stronger than many steels. Light, rustproof. Williams quality throughout. This 'ghost ring'aperture is available as an accessory item, whoich is compatible with the standard Williams WGRS, WGOS and WDOS sights. Replace the standard aperture with this ghost sight for quick target acquisition and faster shooting. FeaturesCompact Low ProfileLightweight, Strong, RustproofPositive Windage and Elevation Locks