Meprolight M-21 1x 30mm Red Dot - 4.3 MOA - The M21 Self-Illuminated Reflex Sight is used and trusted by militaries and law enforcement agencies worldwide. It is designed and manufactured to the highest military standards to assure years of reliable operation under all field conditions. With no switches, no battery or other external sources of power, the sight is always ready for action. A red dot sight with fiber-optic illumination by day, Meprolight tritium by night, it takes charge of any battlefield with no need for batteries, ever. Its rugged, battle-proven construction meets or exceeds rigorous MIL-STD-810 standards to thrive in the harshest conditions, with five available reticles and a big 30-millimeter lens for maximum situational awareness.