Machined with certified USA 7075 T6 billet aluminum and held to an extremely tight tolerance of .0005 inches using a precision Computer Numeric Controlled (CNC) mill. These Vortex rings are then serialized, vibratory tumbled, bead blasted and finished with a Type III hard coat anodize. Rugged, lightweight, anti-snag design Robust, Grade 8 fasteners 100% made in USA guaranteed for life Available Precision Matched 30mm Rings MPN Height Optical Centerline PMR-30-87 Low 0.87" PMR-30-97 Medium 0.97" PMR-30-97-W Medium Weaver 0.97" PMR-30-126 High 1.26" PMR-30-145 High Plus 1.45" Learn More About Vortex Precision Matched Rings Vortex Precision Matched Rings (Set of 2) for 30mm (1.45 Inch /36.8 mm). PMR-30-145