This is a combo set of UTG Leapers flip-to-side magnifier and UTG Leapers 6 inch red/green T-dot sight. Both the magnifier and red T-dot sight have quick detach mounts to fit a 20mm picatinny/weaver style rail and the center height of both is 40mm from the base to the center of the optic so that they are in perfect alignment when used together. With this set you get a crisp clear reticle when looking through the magnifier and a full field of view, the built-in sunshade on this red dot sight reduces glare and coincides perfectly with the magnifier. these two products were specifically made to be used as a set. The magnifier slides back to unlock and flip to side allowing it to clear the sunshade on the scope and will fit perfectly inside the sunshade when locked in the upright position.