The HOLOSUN 509TX2 is a good closed red dot not only for pistol use, but can also be used for a rifle set up wether stand alone mounted, piggyback option , or also for a low mounted shotgun sight utilizing a dedicated mount. The optic comes with an RMR adapter plate. (Features) It has 10 daytime brightness settings, 2 NV settings, and takes a side loaded 1632 battery,