This AIM-O brand "Reflex" type red dot screw in DE version is a reproduction of Trijicon's RMR screw (Ruggedized Miniature Reflex). It has a red dot adjustable in elevation, in deactivation, and can be activated with the ON ( + ) and OFF ( - ) buttons.
Beware, for the startup after insertion of the battery, you will just have to remain pressed for about 6 seconds on the + button of the intensity selector!!