This is a FDE version of the popular HS503GU. The HS503GU is a micro red dot optic equipped with a 65 MOA circle dot reticle with the option of switching to a 2MOA dot only. The “G” signifies that the battery is side mounted on the side of the optic. The “U” signifies a housing design that shrouds the windage and elevation turrets on two sides. Employing new LED technology, the life-time for one CR2032 battery can reach 5 years on the 2 MOA dot. Holosun’s “Shake Awake” technology automatically turns the optic on at the slightest movement. When the optic senses no movement, it will go to sleep.