The Burris Optics F3 Flattop Fast Mount is a Weaver/Picatinny-style mount for the Fast-series red dot sights. It mounts onto Weaver/Picatinny-style bases and offers protection to the side of your sight while still allowing easy access to illumination controls. There are also compartments for carrying a spare battery, an open-end wrench, and a Torx wrench..