The Radian GUARDIAN Optic Mounting System provides unprecedented protection for your pistol red dot optic. Machined from 7075 aluminum & hard anodized, the design provides top/ front/side impact protection. Optional back-up sights, provide an unobstructed, irons forward sight picture. The STUD-LOK threaded stud/nut mounting interface is the most secure system on the market. This provides much longer thread engagement, greater hold down power, with increased shear resistance. TRU-SEAL eliminates the need for an added sealing plate. Pre-installed O-rings on the mounting screws hold the plate watertight to the slide, sealing out moisture, eliminating corrosion in the mounting threads.