The Ultralux 4x20mm scope and mount is specifically designed to withstand the rigors of the Ruger Mini-14 & AR 15. Installs in minutes by substituting a special dovetail side plate for the factory side plate (no modifications to the gun are required). The scopes have a built-in bullet drop compensator calculated for the trajectory of the M193 ball round and has settings for 100, 200, 300, 400 and 500 yards. The scopes are Nitrogen-filled and are fogproof, waterproof, and shockproof to give you a lifetime of dependable service. Limited lifetime warranty.