The HS503CU is a 20mm micro sight designed for rifle and carbine applications. HS503CU features Holosun&';s Solar Failsafe technology and our Multi-Reticle System (MRS) which includes a 2MOA dot and a 65 MOA Circle. Holosun&';s Red Super LED allows for up to 50k hour battery life with 10 daylight and 2 night vision compatible reticle intensity settings. The HS503CU housing is made from 6061 aluminum and includes both a lower 1/3 co-witness mount (1.63") and a low mount (.75") for low-comb height rifle applications. Additional features include Shake Awake technology, rubber lens covers, and a side battery for the 2032 battery. HS503CU is a versatile sight for users of all levels. Features: Holosun&';s Solar Failsafe Technology is an innovative feature pioneered by Holosun in red dot sights. Solar Failsafe allows the red dot sight to remain powered when your battery fails. Superled, the brightest environments down to no-light situations Multilayer Reflective Glass Titanium Housing In The Box: Lower 1/3 Cowitness Mount Low Profile Mount T10 L Key Rubber Cover User Manual CR2032 Battery Lens Cloth