Feature A Tactical Offset Style A Mil-spec Finish A 30mm Diameter Picture Specification A Diameter: 30mm A Overall length: 135mm (5.3 inch) A Ring gap length: 64mm (2.5 inch) A Ring width: 16mm (0.6 inch) A Base length: 80mm (3.1 inch) A Weight (net): 190g (6.7 ounce) A Height: 38mm (1.5 inch, from bottom to the center of ring) A Fit on 21mm picatinny rail A Mil-spec finish A High quality aluminum alloy in durable black matte finish A Shock proof can be used on real fire caliber