As a firearm instructor I have used my share of laser bore sights and this is actually one of the better ones of its type. I say of its type as muzzle mounted bore sights will seldom be as accurate as ones fitting in the chamber of the gun. However, for its type it really works well. The CR2 batteries are way better than the tiny coin cells that are tricky to insert and turn the unit on as soon as inserted in some models. The range of caliber adapters is very good (avoiding large jumps between adapters that make for loose fitting and thus inaccuracy) and means you don't need a bunch of separate bore sights of the chamber-fitting type if you are working with multiple calibers. Finally, the positive on/off switch gives a healthy click to let you know it has been turned on or off. Overall, a great little bore sight for the price - I'd recommend it to my students or any other shooters wanting a single bore sight fora number of different firearms.