Lyman 66 Receiver Sights are used with flat receivers. They feature 1/4 minute audible click micrometer windage and elevation adjustments as well as coin-slotted low-profile stayset knobs. The quick-release slide with return-to-zero preset screw allows quick removal and replacement. Includes two interchangeable aperture discs: a large hunting aperture and a small target aperture. Black anodized aluminum body with blue steel knobs and detents. Notes: Some Marlin rifles made after 2000 may not be drilled and tapped for this sight. Please check to see if your gun is drilled and tapped before ordering.FeaturesAudible click micrometer adjustment for elevation and windageQuick-release slideCoin-slotted knobsTwo aperture disks (large for hunting and small for target shooting)