The Mepro M22 PRO features a factory-installed light module that eliminates reticle washout and enhances low-light performance. With cutting-edge fiber-optic illumination for daylight visibility and premium Swiss-manufactured tritium vials for nighttime clarity, this sight operates seamlessly in any lighting condition- no batteries required (unless you want it).Tritium glows at a certain brightness level 24/7/365. Meprolight engineers designed a battery powered mechanism to enhance the reticle in extremely lowlight. The single CR2032 battery provides over 50,000 hours of use. The auto-adjuster reacts to ambient light to maintain a crisp reticle in the worst conditions. Do you need it for the M22 to work? No. It is there to mitigate the effects of adverse conditions. The transition between fiber-optic and tritium systems is instantaneous and automatic, ensuring you're always ready. Built with rugged, battle-proven construction, the Mepro M22 PRO meets or exceeds rigorous standards to...