When you need to sight in your rifle or slug gun, Bushnell's Professional Bore Sighter gets you on target in a hurry. Simply look through the scope and center the reticle within thhe bore sighter's grid. Remove the bore sighter, and you're ready to make final adjustments by shooting. Should you drop or bump your gun while hunting, the bore sighter can also tell you if the scope is still zeroed. Comes with a leather carrying case. About $100 for the bore sighter, $20 for each arbor (arbors available for 12-gauge shotgun and rifles from .22 to .45 caliber).