The AR-F4 FastFire Mount is the simplest and most effective way to mount any FastFire sight on an AR flattop. The AR-F4 allows the Fastfire to mount at the optimum height so the red dot can co-witness with flip-up sights. Metal wings protect the lens from impact and unintentional abuse. Lower compartment stores spare battery, open-end wrench, and Torx wrench. Fits Weaver or Picatinny-style bases. Burris AR-F4 Mount for FastFire Reflex Sights 410347