HRT SL (Super-Low) Series Rings, precisely machined from an aluminum billet, with tolerances held to .0002″, give maximum scope/ring contact. Holds scope securely against recoil. Four-screw cap lets you align the reticle, tighten the left side of the cap, then the right side without the scope rotating. Radiused edges and corners help prevent snagging while providing an attractive appearance. Large, clamp-nut lets you torque rings to Mil-STD 1913 (Picatinny) bases. SPECS: 7075-T651 Aluminum Alloy, matte black, hard anodized to Mil-A-8625 standards. 5/8″ (15.8mm) wide. Height measured from the top of base to center of the ring. 30mm – Super Low: .820″ (20.8mm).