The GUARDIAN is the strongest optic mounting system on the market. TRU-SEAL eliminates the need for an added sealing plate. 0-rings on the mounting screws hold the plate watertight to the slide, sealing out moisture, eliminating corrosion in the mounting threads. Designed to mount to Glock MOS for Trjicon RCR optic. Our 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.