Pre zero your scope with the Nikko Stirling scope aligner. The scope aligner safes your time and money. Less shots and less time for sighting in your scope. Each aligner is supplied with 16 barrel arbores that should suit most rifles. After mounting your new scope simply insert the correct barrel arbour into the devise and insert into barrel to adjust your scope. Test shooting with live ammo on a shooting range is recommended before firearm is used in the field. Features: Rugged ABS carry case Small size 16 barrel arbores Suits most rifles