The RugerA(R) ReadyDot(TM) is an ultra-reliable 1X reflex sight designed specifically to co-witness with the RugerA(R) MAX-9A(R) pistol, but the low profile sight fits any compact handgun with a standard Shield RMSc footprint. It is a fixed, non-adjustable sight with a large 15 MOA dot optimized for rapid target acquisition at pistol distances. The fixed co-witnessed dot avoids the necessity for delicate adjustment mechanisms making this one of the most rugged and reliable, waterproof and shock resistant pistol optics available. HOW TO USE THE READYDOT(TM) SIGHT When using your RugerA(R) ReadyDot(TM) sight, it is important to keep both eyes open. Look directly at the Mfg: Ruger