Best reflex sight in the market hands down. - Aimpoint ACRO P-2 Red Dot Reflex Sight

The aimpoint acro combines durability, reliability, and long battery life in a single package. One concern is that the sight picture isn't as large as other optics. The ACRO stands as probably the best and one of the most combat proven optics on the market. No concern or gripe about it other than the relatively small sight window, which is to be expected. Also the proprietary mounting system is a bit irritating, and it sits way too high for most guns and it's hard to find ironsites that cowitness unless you buy the gun fully assembled.

The red dot can also get very very very bright if you need it to, a common gripe on budget red dots.