Leupold standard rings are engineered to match up with STD 1-piece and STD 2- piece bases. Extension ring sets give you 5/8" of additional ring spacing adjustment, so you can shorten or lengthen your ring spacing on rifles. STD rings are precision engineered to match up with STD 1-piece or STD 2-piece bases. Rear ring is secured by windage adjustment screws. Available in five different ring heights. Machined steel construction. Features: Forged and machined steel construction Versatile, and available for many different rifles The forward part of the base accepts a dovetail ring, locking it solidly into position, the rear ring is secured by windage adjustment screws Long range STD mounts provide a 15 MOA slope of built-in elevation compensating for bullet drop at extreme ranges 2-piece bases offer maximum accessibility to the breech area of your rifle 2-piece bases fit right and left-hand actions, and reversible bases are available for many actions STD rings are engineered to match up with STD 1-piece and STD 2-piece bases, five different ring heights are available for STD bases