The Wheeler Engineering Scope Ring and Lapping Kit Combo allows you to properly install a scope on a firearm. The alignment bars in this kit provide for perfect alignment of both rings and will also diagnose any misalignment problem" vertical or horizontal" giving you the opportunity to fix the problem before damaging the scope or experiencing frustration at the range. The lapping bar is used to lap the rings to improve alignment" reduce stress on the scope and improve the grip of the rings on the scope. It also serves as a lever to rotate dovetail rings into place. Lapping the rings can also minimize or prevent ring marring of the scope.