This is the standard multi-reticle finder that allows the user to switch from a red dot to a crosshair, circle or larger red dot. The lever on the back is used to change reticle patterns. Brightness is the same as standard MRF finders from other sources and is designed for daytime use. For nighttime use turn it down to the lowest setting. This finder uses the standard rifle scope dovetail base. To mount it to your telescope use one of the various F2 finder bases. The MRF attaches to one of our bases using an Allen wrench.