Manufaturer Part Number: SORX1600The Sig Sauer SIG-LOC(TM) (Leverage Optimized Connection) system was first concepted during the development of the ROMEO-M17 revolutionizing pistol-mounted optic integration with a low-profile ultra-tough connection between the optic and pistol slide. Designed for precision and strength SIG-LOC(TM) ushers in a new era of expectation and performance for civilians and professionals with the ROMEO-X SIG-LOC pistol-mounted red dot.SIG-LOC(TM) is an innovative mounting footprint that establishes five points of contact between the slide and optic to eliminate shift in zero created by extensive shock from recoil and harsh impacts. The unique bottom-mounted design allows for a longer focal length that dramatically reduces parallax and reticle distortion to provide an incredibly forgiving shooting experience.With SIG-LOC(TM) you're investing in technology that has been vetted and trusted by the most demanding users in the world ensuring superior accuracy and reliability in every situation. Inspired by Mil-Spec ROMEO-M17 Establishes 5 total points of contact to create the strongest lockup in the industry Longer focal length to dramatically reduce parallax and create an ultra-crisp reticle Rugged 7075 aluminum housing with a fully enclosed and sealed optical system Distortion-free aspherical glass lens MOTAC (Motion Activated Illumination) Industry's lowest deck height for standard-height iron sight Co-Witness Available Reticles: 3 MOA Red Dot 6 MOA Red Dot or Circle Dot 20000 hour battery life with side load battery 15 illumination settings including 3 dedicated night vision Assembled in USA Fully back by INFINITE GUARANTEE