Sorry for such a newb question, but I cannot get the search function to cooperate tonight.
Why two apetures on the "L" shaped bar that rocks forward and rearward on the rear iron sights on the AR15? Are they different sized openings, or is one higher than the other for further distances?
Why two apetures on the "L" shaped bar that rocks forward and rearward on the rear iron sights on the AR15? Are they different sized openings, or is one higher than the other for further distances?




















































