This sight set is made from 6061 aluminum and mil-spec hardcoat anodized for durability.Sights lock in both deployed and folded positions.The spring mechanism is quite durable and completely concealed to prevent fouling from dirt.The flip-up front sight is hk configuration.The a2 flip-up rear sight has a dual aperture with a conventional large and small aperture.The sight deploys with the large aperture.It is not intended for lower height gas block rails.M4 cowitness height.Type: Flip Up Front/RearFrame Material: 6061-T6 AluminumFrame Color: Black AnodizedFirearm Fit: AR-15Base Configuration: Picatinny RailStyle: Flip Up Back Up Sight SetFront Material: AluminumRear Material: AluminumWindage Adjustment: AdjustableElevation Adjustment: AdjustableFirearm Type: AR Platform