I have the trijicon rmr, Burris ffII, and primary arms micro green dot. Trijicon is the best one suited for the gun, it's more rugged and doesn't need to be removed for adjusting the sights. The other two have the locking screws that get blocked by the rear sight. I use the fast fire on an offset mount on my ar15 and the primary arms on my ruger 22/45
You can never have too many guns....
Docter 2 on mine. No issues thus far...came in a brownish finish which matches the FDE. Paid $230 for mine. I know Trijicon was a lot more expensive.