Leupold BackCountry, 1 Piece Base, Fits Weatherby Vanguard Short Action, Matte Black 171514 Leupold BackCountry cross-slot bases are made of 7075-T6 aluminum, making them some of Leupold's lightest and most rugged mounts yet. This BackCountry cross-slot base is designed to fit a Weatherby Mark 5/Vanguard Long Action and accepts both Picatinny- and Weaver-style rings