The Holosun ARO (Advanced Rifle Optic) Red Dot Sight is an advancement on the popular Holosun 20mm 403 and 503 series optics. The ARO features an all-new 22mm housing design that mates perfectly with Holosun magnifiers and includes an all-new 1.63" lower 1/3 co-witness pedestal mount. ARO is available as a 2MOA dot only or with the Holosun Multi-Reticle System (MRS) in Red, Green, or Gold. Up to 50,000 Hour Battery Life Shake Awake Technology with Last Setting Recall IP67 Waterproofing 50 MOA Travle Range 10 Daylight and 2 Night Brightness Settings 0.866" Window Size