The Meprolight Mepro21 Reflex sight provides constant, all-light aiming capability, without batteries. Designed through close collaboration with Israeli Special Forces, the Mepro21 was the first reflex sight in the world designed for close quarter combat. Reticle illumination is achieved by a protected fiber optic light collector system during the day, and by a miniature self-powered tritium light source at night. Transition between the two systems is instantaneous and automatic to assure good contrast between the aiming dot and the target area. The Mepro21 features a large 30mm diameter lens which allows rapid target acquisition with both eyes open. This reflex sight offers shooters the ability to acquire targets accurately at any range in any situation with both eyes open. It is also designed to work with a magnifier. Quick detach Picatinny mount included. The Meprolight Mepro21 is battle proven, reflexive to use, deadly accurate, and life dependable.