ARO (Advanced Rifle Optic) is an advancement on our popular 20mm 403 and 503 series optics. ARO features an all-new 22mm housing design that mates perfectly with our magnifier series, an all-new 1.63 lower 1/3 co-witness pedestal mount, and compatibility with a new lens cover and anti-reflection device system (available separately). This combo package features the ARO-RD2 and HM3X in a hard case. Specifications for Holosun ARO Advanced Rifle Optic 1x22mm Reflex Red Dot Sight w/HM3X Magnifier: Manufacturer: Holosun Color: Black Fabric/Material: Aluminum Magnification: 1 x Objective Lens Diameter: 22 mm Reticle: 2 MOA Dot Illumination Type: LED Illumination Color: Red Brightness Settings: 12 Eye Relief: Unlimited Adjustment Click Value: 0.5 MOA Battery Type: Lithium Metal, CR2032 Battery Life: 50000 hours Water Resistance Level: IP67 Red Dot Sights-Footprint: Not Applicable Package Contents: Holosun ARO Advanced Rifle Optic 1x22mm Reflex Red Dot Sight w/HM3X Magnifier