Sighting in your rifle just got way easier and saves ammo. This laser bore sighter is specifically chambered for .300 Winchester Magnum rifles. You just insert the laser (battery included) into the muzzle, turn it on, and it projects a crisp red dot onto your target. Align your scope's crosshairs with that dot at a short distance, and you'll be on paper at the range. It mounts right in the barrel, no tools needed. From TB Accessories, it's a simple, effective tool for hunters and shooters to get a rough zero before live fire. Make range trips quicker and less frustrating. A handy gadget for any rifle owner's kit.