Our bases are strictly held to tighter tolerances than allowed under the Picatinny standard (MIL-STD-1913), ensuring complete compatibility with all Picatinny style, as well as Weaver style scope rings.They are available in a natural, satin silver finish (bead blasted), or with an incredibly tough black finish called GunKote. Mil Spec 1913 Rail for solid mounting 6061 Aluminum Type 3 Hard Coat Anodized Easy install, one piece construction Includes mounting hardware Zero MOA cant Fits right or left hand action