The HS503R is a small compact micro red dot optic that features Holosun's Rheostat Dial to adjust brightness settings. Employing Holosun's LED technology, The HS503R can achieve constant on battery life of up to 100,000 hours on medium setting. This optic features Holosun's proprietary Multi-reticle System (MRS) giving the user 2 reticles to choose from.