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. 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.SIX back-up sights (BUS) seamlessly integrate into the Guardian Optic Mounting System providing rapid, reliable, and precise target acquisition in scenarios of red dot optic malfunction. Featuring anti-glare, anti-snag and ultra low co-witness design, SIX sights lie inconspicuously in wait until you need to deploy them. Like a wingman when things aren't going as planned, SIX has your six.MATERIALS: 7075 Aluminum Type Ill Hard Anodized Guard/Plate Custom Machined SS Fasteners with Oversized Torx SocketsINCLUDES:2 - Plate Mounting Screws 2 - TRU-SEAL 0-Rings 2 - STUD-LOK Studs 2 - STUD-LOK Self-Locking Sleeve Nuts