Holosun HS503GU 1X20mm Circle Dot Tactical Hunting Shooting 2 MOA Red Dot and 65 MOA Circle Reticle Gun Sight;

HS503GU is a red dot sight that features the circle dot reticle. G signifies that the battery is in a round, screw-on turret on the outside of the optic. U signifies a housing design that shrouds the wind age and elevation turrets on two sides. Employing new LED technology, the life time for one CR2032 battery can reach 2 years if left on constantly. However, the motion based automatic on and off feature extends the battery life dramatically beyond that for the average shooter. Red Dot Lens Positioning. All red dot sights have an objective lens at the front of the unit that is spherical in shape. However, unlike a conventional rifle scope, the objective lens in a red dot sight is positioned off axis and appears to be tilted when looking at the sight. This angle of the front lens allows the light generated by the battery powered LED light source inside the unit to be reflected back into the sight. The reflected light becomes the "dot" or aiming reference that the user sees when a red dot sight is switched on. This engineered "bending" of light is what makes today's red-dot sights so popular and easy to use. Adhesive is used on the inside of the sight to secure the LED to the inside of the tube. By design, the LED package intrudes slightly on the field of view.