The Swampfox Justice II is an open-emitter reflex sight built on the RMR footprint, with an oversized 30mm round window for fast target acquisition. It projects a 6 MOA green dot and works on RMR-cut pistol slides as well as RMR-pattern rifle mounts. Features: Open-emitter reflex red dot with oversized 30mm round window 6 MOA green dot for fast acquisition RMR footprint - fits RMR-cut slides and RMR rifle mounts 7075-T6 aluminum housing with multi-coated lens 10 brightness settings Shake 'N Wake automatic on/off Top-loading battery tray RMR footprint fits a wide range of large-frame pistols and RMR-pattern rifle mounts. Verify your slide or mount is cut for the RMR footprint before ordering.