Barska Boresighters
BARSKA's 15 Piece Boresighter Kit will ensure that your rifle is accurately zeroed when you’re testing out a new rifle and scope combination. This Boresighter fits snugly in the rifle barrel to eliminate any “play” that can result in an inaccurate boresighting adjustment and poor shooting accuracy.

How a boresighter works
Model AW11076 Insert stud into boresighter and insert other end into barrel. Align internal grid. Scope is now pre-zeored.

Caliber
Caliber (Cal.) is a system of measurement for the internal bore diameter of a rifled-barreled firearm (rifle or pistol) based on the decimal part of an inch (.22 Cal) or in millimeters (9mm). American caliber designations refer to the distance from land to land, not groove to groove.