I have the Trijicon RMR RM06 too. It has adjustable brightness which sort of balloons the dot to make it appear bigger when turning up the brightness. It has a 3.25 MOA red dot. Some people say that it's too small but it is perfect for me. If you want it bigger just turn up the brightness and it will look bigger. For me, I like the smaller dot because you can be more precise. With a larger dot, people say you can get it on target faster but you lose the precise shot placement. The RMR DOES CO WITNESS with the stock sights.