Designed through close collaboration with Israeli Special Forces, the M21 uses a fiber-optic light-gathering system during the day and self-powered tritium at night to ensure a bright aiming point around the clock. No fumbling with batteries or switches. Day or night, no matter the weather, the Mepro M21 is ALWAYS on and ALWAYS ready. The large 30mm display window allows you to keep both eyes open for better battlefield awareness, and the orange bullseye reticle makes for ultra-fast targeting on targets at a wide variety of ranges. It's no surprise that the M21 is used and trusted by militaries and law enforcement agencies worldwide. Self-illuminating design requires no batteries of any kind Fiber optic light-gathering system provides operation during the day Self-powered tritium vial provides operation at night Orange bullseye reticle 30mm display for wide field-of-view Mil-spec quick-release mounting system Attaches to standard MIL-STD-1913 rail MIL-STD-810 qualified Armored design for combat use 1 MOA adjustments for windage and elevation Order today!