ACD, or Anti-Cant Device, is manufactured and marketed by Mounting Solutions Plus. Mounting Solutions Plus defines “cant” in terms of shooting as,”the result of a rifle being held off the perfect vertical plane in which it was zeroed. Cant results in rotation of the sights off the true vertical plane.” The device, in a nutshell, is a visual indicator of level which is mounted on a riflescope. Physically it is nothing more than a spirit level mounted into a low profile scope ring.