Deep-well aperture fits the AR-15 A2 rear sight and provides 11 aperture settings (.022"-.125") to ensure excellent sight focus and contrast in all light conditions. Positive click adjustment between each setting by simply turning the flexible rubber light shield. Adjusting the aperture diameter will not change your point of impact but will increase your depth of field and bring your front sight into a clearer focus. Installs with simple tools; includes required mounting hardware.
Sinclair, Issue:4A, Page:215