The M21 Reflex sight provides constant, all-light aiming capability, without batteries. Designed through close collaboration with Israeli Special Forces, the M21 was the first reflex sight in the world designed for close quarter combat. It is battle proven, reflexive to use, deadly accurate, and totally reliable. Standard Sight on Israeli Military Tavor and M16/M4 rifles. The M21 features a large 30mm diameter lens which allows rapid target acquisition with both eyes open. 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. 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. The M21 is the optic of choice for the Israeli Defense Forces. Always ready for action – no batteries or switches. Reflexive, parallax-free aiming with both eyes open and focused on the target. Self-illumination adjusts to ambient light. Reticle designed to be visible under all conditions. Operates under all weather and temperature conditions. Night Vision Compatable Large 30mm diameter lens with state-of-the-art coatings assures large FOV. Armored design for hard combat use. Sight is black and grey, no white or bright colored fiber optic tubes exposed. Increases accuracy and speed when firing under pressure. Quick-release Picatinny mount retains zero.