Used on what firearm and for what distances?? I set up a M&P optic ready pro with a trijicon dual illumination model with a 9" green dot. The dot sets right on top of the tall sights on the pistol. That's gives a 4 1/2" dot at 50 yards and 2 1/4" at 25. Needs no battery and will serve for both CC and fun with some match use .
I have used and still use battery powered 2 moa dots on hunting revolvers good for palm of your hand groups at 100 yards. I'm not one that likes any electronic as a primary on a rifle /carbine . Give me a 1-4 or 1-6 any day, add a lighted reticle if you got to have one. Now if your wanting reflex style, if on a carbine you might also look at mepro 21. mor or m5. These large units that use batterys can last up to 8000 hours and changing batteries just ain't that big a deal to me.