Leupold steel Standard (STD) rings and bases represent the most adaptable mounting system available. This particular model is designed to fit a Browning BAR and is ideally suited for Standard calibers below .300 Win Mag. STD rings are available in five distinct heights and are precisely engineered to align with STD 1-piece or 2-piece bases. The front dovetail ring allows for lateral adjustment through the rear windage screws during bore sighting. Additionally, shims can be utilized to preserve the scope's elevation adjustment for BDC (bullet drop compensation) dial applications. The connection between your scope and firearm is of utmost importance, which is why our mounts are as robust and reliable as the Leupold optics they support. With an extensive range of mounting systems to choose from, you are certain to find the perfect fit for your firearm and shooting style. Manufactured in the USA and guaranteed to withstand a lifetime of use, Leupold mounts are designed to never disappoint.