Vortex Optics starts with certified USA 7075 T6 billet aluminum and hold it to an extremely tight tolerance of .0005 using their precision Computer Numeric Controlled (CNC) mill. These 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. Rugged, lightweight, anti-snag design Robust, Grade 8 fasteners 100% made in USA guaranteed for life Mfg: Vortex Optics SPECS: Ring heights are measured from the base of the ring to the center of the riflescope tube. Picatinny Style.