red dot type 2

A red dot sight is a common classification for a non-magnifying reflector (or reflex) sight that provides an illuminated red dot to the user as a point of aim. A standard design uses a red light-emitting diode (LED) at the focus of collimating optics, which generates a dot-style illuminated reticle that stays in alignment with the weapon the sight is attached to, regardless of eye position (nearly parallax free).
Red dot sights are considered to be fast-acquisition and easy-to-use gun sights for firearms used in civilian target shooting, hunting, or in police and military applications. They are also used on cameras and telescopes. On cameras they are used to photograph flying aircraft, birds in flight, and other distant, rapidly moving subjects. Telescopes have a narrow field of view and therefore are often equipped with a secondary "finder scope" such as a red dot sight to orient them.

View More On Wikipedia.org