Designed for a 3/8" dovetail rifle rail, the adapter base can be installed and adjusted to give extra elevation angle. After installing on the rail, the rear set screw can be used to gradually tilt the Weaver railtop downwards towards the trajectory of your bullet. A forward position stop ensures the adapter base does not creep down your rail during recoil. This adapter base works to overcome barrel droop or to compensate for extreme bullet drop over long range.