This one-piece aluminum base is machined to tight tolerances for a custom fit. It offers maximum strength for rings to hold tight. Screws are included. Fits Browning bolt action BBR, Hi-Power, other caliber (older models); Colt 57; H&R 300, 301, 330 & 370 (Pre 1973); Knight KRB7, LK-93, Wolverine, Legend, Disc, American, Revolution; Weatherby FN Mauser style actions.