Simplest, most effective way to mount any FastFire sight on flattop; Allows the FastFire to mount at the optimum height, so the red dot can co-witness with flip-up sights; Fits Weaver or Picatinny-style base; Metal wings protect the lens from impact and unintentional abuse; Lower compartment stores spare battery, open-end wrench, and Torx wrench; Matte Black Finish; Burris Forever Warranty