The LaserLyte .17 HMR Cartridge Laser Bore Sight helps sight-in firearms quickly and economically, getting the user on paper the first shot (3-4 inches from center at 100 yards). The ingenious design of this cartridge bore tool allows the user to simply slide the unit into the chamber of the firearm. When the bolt is closed the tool automatically activates. This remarkable laser may be the smallest of its kind ever created and makes quick work of sight-ins for this extremely popular round. The .17 HMR Cartridge Laser Bore Sight is powered by four 348 batteries that provide at least one hour of continuous on. Manufactured to the highest degree of .17 HMR match grade tolerances, each unit is checked with LaserLyte's custom-made gauge. Whether it is initial sight-in or checking to see if the firearm is still on target, both can be achieved while saving time and ammo.