To my understanding, the center of all the apertures are on exactly the same plane. Elevation for whatever distance you wish is set with the front sight and the windage is set with the rear. The zero distance is determine by you and your intended use and the ammo you will be using. The different apertures on the rear sight are just personal choice for your individual eyesight. The Largest aperture allows the most light in and the largest field of view, while the smallest aperture will normally allow the greatest precision.