Notes: The adapter plate for the "-R" version is compatible with the most popular aftermarket slide cut in the industry. It is the same footprint as the Holosun 507C, making it compatible with most plate systems found on factory optics ready guns like the Walther PDP, S&W M&P C.O.R.E., CZ Optics Ready, Agency Arms AOS, FN 509 MRD, and Springfield Armory XDM Elite series handguns. The included 509 adapter plate is not compatible with ZEV or Shadow Systems style RMR interfaces. The 509 ACSS model does not share the same footprint as the 509T (non-ACSS models) and therefore is incompatible with aftermarket mounting solutions and custom cut slides for the 509T (non-ACSS models). The ACSS Vulcan reticle provides a large circle guiding the eyes towards the 10 MOA center chevron. If you are off-center, a portion of this outer circle will appear in the window to give you an instant reference on how to get centered. The circle phases out of the sight window completely when the center chevron is properly aligned in the sight window. Don't need the circle? It can be easily deactivated. The Holosun HE509 Red Dot Sight uses Solar Failsafe technology to power the optic and uses patented Shake Awake technology which senses motion to power the sight on and off. In addition, it “recalls” your last setting and makes sure you don’t lose those customized settings once the sight system turns off. The Holosun HE509 Red Dot Sight offers up to 20,000 hours of battery life. All versions of the Holosun Red Dot Sight system are projected from the same LED, so you don’t have to worry about having to re-zero when changing reticles. NOTE: This optic is not intended to allow co-witness of fixed iron sights EXPORT CONTROLLED ITEMS: These items are controlled for export and may require an export license from the U.S. Government. Buyer acknowledges that Buyer is responsible for obtaining all export licensing authorizations and filing all export documents prior to export from the United States.