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Meprolight M21 Open X Day/Night Tritium Illum Reflex Sight w/Picatinny Rail Adapter 0626610

SKU 0626610-MPL

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Mepro takes red dot sights to the next level with the M21! This advanced sight was developed for the IDF, and is highly suited for close-quarters or in situations where the use of both eyes is critical. The M21 functions without batteries, and provides illumination with a system of fiber optics and tritium. The fiber optic collectors on the top and front of the sight illuminate the reticle in daylight conditions, while the self-powered tritium illuminates the reticle in the dark. Transition between the two illumination systems is seamless, and is always available without any switches or external sources of power. In addition, the M21 is available in the following reticles: Bullseye, Triangle, Open X, or a dot reticle in either 4.3 MOA or 5.5 MOA.

Features of the M21 Red Dot Sight:

  • Functions without batteries
  • Self-illuminated via system of fiber optic collectors and tritium
  • Available reticles: Bullseye, Triangle, Open X, or a dot reticle in either 4.3 MOA or 5.5 MOA.
  • No switches or external sources of power


  • Magnification Range:1x
  • Reticle DetailsOpen X Reticle
  • Dimensions:4.48" x 2.16" x 2.75"
  • Weight:13.12 ounces
  • BatteryN/A (tritium and fiber optics)
  • Battery TypeTritium & Fiber Optics
  • Night Vision CompatibleYes
  • Product TypeReflex Sight/Red Dot
  • Item ConditionNew
  • UPC879015004378
  • MPN0626610

Customer Reviews

Average Rating
May 27, 2022

These are very sturdy and well made reflex sights, like any reflex sights, there is some washout in very bright sunlight. This can be solved using the screw on sunshade and buying the REM 21 LED illuminator addition for under $40. I sighted both of mine, one on a Galil ACE and another one in a TAVOR at 100 meters. I have not encountered significant parallax problems that are any different from other equivalent sights. For a flat shooting .223 round you do have to remember that the Mepro 21 line of sight will be about 2 inches higher than the rifle bore, that said the ballistic convergence point if sighted to be 2 inches below zero at 25 yds should be the roughly the same as 100 yds with the line of sight (also about 2 inches low). Whatever the ballistic curve is if sighted in at a 100 yd zero will have to take into consideration bullet rise before and after 100 meters within the Mepro21 plane of sightbeing 2 inches higher than the bore..

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May 27, 2022

The reviewer complaining about this sight being worthless when aiming into a bright area from a dark area is spot-on. I purchased Mepro adjustable polarizers for my two M21 sights and it solves the problem. My main complaint is that the sight has a very high level of parallax and, despite manufacturer's claims of "no parallax", the claims are lies! (Do some online research for a couple of very well-run tests). The Mepro sight is, in my experience, one of the worst sights for parallax, rendering it a close range sight only (under 100 yards) for me. You still must put the reticle in the same place in the window at 100 yards, or you'll typically get 2-3 inches of error from just the parallax! Clamp your gun in a gun vice and try bobbing your head around behind it while sighting at 100 to 200 yards or so. You'll see the reticle move all around on the target. On the upside, the tritium lasts a very long time. My two sights are still very bright after a bit more than 10 years, which is far more than I can say for my similarly-aged Trijicon RMRs. Their tritium is just about worthless now.

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December 14, 2021

Purchased for a in home PDW, no on/off ready to go was my big draw. My particular points of entry all funnel into the kitchen where I keep a light on. Thought process is I'm concealed at end of dark hallway that leads Into master bedroom while intruder is well lit entering hallway from kitchen. This exposes the only flaw I have experienced with this sight, while In the dark looking into light the washout basically makes the sight useless. In the day light it's great, in the dark it's great, from the light looking into the dark it's great. Just a no go from dark looking into light. Will keep sight and just move to another platform with a different purpose.

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