The Aim-O Holographic Red Dot 551 sight is a replica of the famous EOTECH sight. A holographic red dot sight is seen as the best option for use when shooting with 2 eyes open. Fits all standard Picatinny rails. The PCS Holographic Red Dot 551 sight can be set in 2 different colors (red and green). The reticle can also be adjusted in terms of brightness in different strengths. You can fully adjust the sight when there is a deviation (both horizontally and vertically). Operates on 4 LR44 batteries (not included).