Each Weaver base is machined to tight tolerances for a custom fit. These Aluminum bases offer maximum strength for rings to hold tight. Fits CVA round barrels and receivers, post 1996 CVA Optima Traditions Whitetail octagon receiver Traditions in-line Buckhunter round receiver, Pedersoli & Timber Ridge ML Winchester X-150 muzzleloader & Apex 209 Includes custom-hardened fastening screws for mounting.