The MIL-SPEC Mepro M21 Self-Illuminated Reflex Sight is used and trusted by militaries and law enforcement agencies worldwide. It is specifically unique, in that, no batteries are needed. Illumination of the point of aim reticle is achieved by a fiber optic collector system during the day and by a miniature self-powered tritium light source at night. A large 30mm display window allows the shooter to keep both eyes open for better battlefield situational awareness. The shooter has the option of five reticles - 4.3 MOA or 5.5 MOA dot Triangle, Bullseye, and open X. Day or night, no matter the weather conditions with the Mepro M21, it is always on and always ready. MEPRO M21 is the reliable choice. Designed and manufactured 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. Unique Advantages: 30 mm diameter lens Large field of view Rapid target acquisition Effective use of sight under extreme conditions No batteries. Always ready for action SPECIFICATIONS & FEATURES Magnification x1 Lens Diameter 30mm Field of View Unlimited with both eyes open Eye Relief 10 to 600mm Power source Self Illuminated Aiming Point Diameter 4.3 MOA/ 5.5 MOA/ Triangle/ Bullseye/ Open "X" Dimensions: (L x W x H) 114 x 55 x 70 mm (with Picatinny adaptor) Weight 372 g (with Picatinny adaptor)