The new scope aligner allows you to save time and money sighting in your rifles before a hunt.Each Aligner is supplied with 16 barrel arbors that should suit most rifles and calibers. After mounting your new Nikko Stirling scope simply fit the correct barrel arbor into the device and insert into the barrel. Now looking through the scope you can make adjustments to the windage and elevation to align your scope to the device's targeting grid. Now take the Aligner out of the barrel! Final zeroing at the range can now be completed quickly and safely.