Leupold steel Standard (STD) rings and bases are the most versatile of any mounting system they offer. This specific model fits a Browning BAR and is the perfect choice for standard calibers less than .300 Win. Mag. STD rings come in five different heights and are precision engineered to match up with STD 1-piece or 2-piece bases. The front dovetail ring pivots, allowing for lateral adjustment using the rear windage screws while bore sighting. Shims can also be used, reserving the scope's elevation adjustment for BDC (bullet drop compensation) dial applications. Nothing is more crucial than the link between your scope and firearm. That's why Leupold's mounts are every bit as rugged and dependable as the Leupold optics they secure. And with a huge variety of mounting systems to pick from, you're sure to find the perfect match for your firearm and style of shooting. Made in the USA and guaranteed to hold up to a lifetime of abuse, Leupold mounts will never let you down.