The Kinetic Research Group Night Vision Backbone Mount mounts directly to the 2019 and newer backbones that have the 10 threaded mounting holes at the front of the backbone. It mounts solidly. You can flip the direction the rail points and even shift it forward and backwards to achieve the optimal positioning for your setup. Fits: 2019 and newer KRG chassis with backbones that have the 10 threaded M4 mounting holes at the front Note: Doesn't fit older backbones without the threaded holes; maximum barrel diameter through the mount is 1.15"