Sightmark Tactical Reflex/Holographic Slide to Side Magnifier Increases magnification of accompanying sights for greater sighting range Improved target recognition, especially at medium range distances EOTech and Aimpoint compatible Multicoated optics Waterproof, Fog proof, Shockproof, Lightweight There are screws on each mount that can be tightened or loosened to make sure the mount slides comfortably. There is a diopter adjustment that will help with eye relief.