We start with certified USA 7075 T6 billet aluminum and hold it to an extremely tight tolerance of .0005 using our precision Computer Numeric Controlled (CNC) mill. Our Precision Matched Rings are kept in pairs throughout the manufacturing process ensuring perfection from one set to another. These Vortex rings are then serialized, vibratory tumbled, hand-bead blasted and finished off with a Type III hard coat anodize. These Vortex Precision Matched Rings position the center of the riflescope tube at a height of 0.92 inches (23.4 mm) from the base. Will only work with Picatinny spec mounts will not work with Weaver mounts. Sold two rings per package.