A lot of shooters and gun owners who purchased or built their handgun from the ground up use the tried and true three dot iron sight arrangement. Many of us spend plenty of time at the range attempting to achieve better shot placement. While three dot iron sights are pretty good, the Holosun HE509 Powered Red Dot sight with ACSS Vulcan reticle is almost guaranteed to help you improve your accuracy. This pistol sized Holosun Red Dot Sight straightaway allows for a large field of sight and has those features which allow you to sight in quickly and acquire the target and the location you intend to hit. Whats so neat about the Holosun HE509 is that the entire sight system is fully enclosed in light and rugged aluminum. Built to provide enhanced environmental protection and abrasion and shock protection, the HE509 Red Dot Sight protective housing stands head and shoulders above an open form reflex form factor. Note: 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 revolutionary patent-pending ACSS Vulcan reticle provides a large circle guiding the eyes towards the 10 MOA center chevron, eliminating one of the biggest challenges for shooters new to slide-mounted red dots. 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. This patent-pending reticle function significantly improves sight acquisition. It takes the common frustration of hunting for the center reticle out of the equation. Don't need the circle? It can be easily deactivated to extend the battery even further. The Holosun HE509 Red Dot Sight uses Solar Failsafe technology to power the optic providing the shooter or operator with a consistent, and very reliable point of aim. Another feature you simply dont expect with a lithium powered optic sight such as this is you dont have to worry about turning it on or forgetting to turn it off. The Holosun Red Dot Sight uses patented Shake Awake technology which senses motion to power the sight on and off. In addition, Holosun manufactured this little sucker with a brain that recalls your last setting and makes sure you dont lose those customized settings once the sight system turns off. Worried about battery life? The Holosun HE509 Red Dot Sight offers up to 20,000 hours of battery life. Simply put, we dont think youre going to have to worry about buying a new battery for this sight system for quite a while. All versions of the Holosun Red Dot Sight system are projected from the same LED, so you dont have to worry about having to re-zero when changing reticles. Altogether, the Holosun Red Dot Sight is a much better sight system for your firearm than traditional iron three dot systems. If you want to start hammering that 5X target to shreds and not only hitting what you aim at, but sending that shot exactly where you wanted it to go, The Holosun HE509 Red Dot Sight this is the sight system for you. Specifications for Primary Arms Holosun HE509-RD Enclosed Solar Powered Red Dot Sight: Manufacturer: Primary Arms Color: Black Finish: Hardcoat Anodized Fabric/Material: 7075-T6 Aluminum Magnification: 1 x Objective Lens Diameter: 0.66 - 0.9 in Reticle: ACSS Vulcan Illumination Type: LED Illumination Color: Red Eye Relief: Unlimited Adjustment Type: MOA Adjustment Click Value: 1 MOA Battery Type: Stand Alone Lithium Battery Quantity: 1 Water Resistance Level: Waterproof Shockproof: Yes Fogproof: Yes Gun Make: AR Platform Weight: 2 oz Condition: New Package Type: Box Magnification Type: Fixed Lens Finish: Multi-Coated Quantity: 1 Attachment Type: Slide Features of Primary Arms Holosun HE509-RD Enclosed Solar Powered Red Dot Sight Finish/Material: Aluminum Adapter Plate for Glock MOS Reticle: ACSS Vulcan Illumination Type: LED Illumination Color: Red Brightness Settings: 12 Eye Relief: Unlimited Length: 1.78 Width: 1.22 Height: 1.14 Weight: 2 Oz Package Contents: Primary Arms Holosun HE509-RD Enclosed Solar Powered Red Dot Sight