I've had, and used, Meprolight Reflex 21 sights since they've been available through Kimber. Their quality is superb, having had no failures or problems of any kind. Rugged, consistent return to zero after taking off, and putting back on different weapons... Have used them on Benelli M1014 shotguns, 5.56 and 6.8SPC LMT uppers on Armalite AR15 lowers, Beretta CX-4s in 9mm Storm carbines, Ruger PC4 in .40SW, and Super Redhawk in .44 magnum. Equal in quality to Aimpoint's superb red-dot systems, though of course, not magnified... Beauty in NOT having to use batteries, further straining the supply line... Fiber-optics and Tritium work better than you would believe... New red triangle, rather than old style gold dot, is fabulous. Target acquisition and engagement is swift, sure, reliable, and deadly... Dollar for dollar, the best CQC optic on the market... The new Reflex 21i has double the fiber-optic filament, and is brighter, longer, before the duty of illumination devolves onto Tritium... I have three Meprolights now, and six Aimpoints (ML3s, ML4s, and Micro T-1s, with two 3X magnifiers) I'll be buying more of the Meprolights, as the problem of future battery supply becomes more of a problem. I heartily endorse the Meprolight Reflex 21i system, especially the Meprolight M21i Reflex Sight 4.2MOA Triangle- it truly is worth the investment, especially if your life is on the line...