The Holosun HS503R is a small compact micro red dot optic that features Holosun's new Rheo Stat Dial to adjust brightness settings. The HS503R can achieve "constant on" battery life of up to 5 years on medium setting. Optional 65 MOA Circle Dot or 2 MOA Dot Parallax free with unlimited eye relief Rheo Stat Dial controls and streamlined housing design Low mount and 1/3 Co-witness mount included Adaptable to Picatinny and Weaver rails CNC machining with T6061-T6 aluminum housing. Fits Aimpoint Micro style mounts/footprints. The HS503R has an optional 65 MOA Circle Dot or 2 MOA Dot. The optic also features Holosun's pr Mfg: Holosun