This Boresighter Kit will ensure that your rifle is accurately zeroed when you’re testing out a new rifle and scope combination. The Iron Boresighter system uses a 15 -piece arbor set that ranges from .177 to .50 caliber and ensures precise bullet placement from the get go. This boresighter fits snugly in the rifle barrel to eliminate any “play” that can result in an inaccurate boresighting adjustment and poor shooting accuracy. Backed by BARSKA’s One year warranty.