The Axeon Second Zero is a precision optical device that gives any rifle shooter an instant additional zero distance whether in a hunting or tactical application. Its an aiming device used in conjunction with your shooting optics and works with all optical sights from rifle scopes to dot sights. The prism driven optical device simply mounts forward of a traditional scope, red dot, acog, or other optic. When engaged, the prism, can be selected based on a hunters specific ammunition load, and shifts the image to compensate for bullet drop. Simply place the crosshairs on the target just as you would at 100 yards. This model is a bell mount for 50mm scope objectives for distance of 330 yards.