Review on Accurately Sight In Your Shotgun With The Sightmark Red Laser Boresight by Thong Pilla

Not only are these more precise as they're loaded into the chamber, they're very accurate as the red dot position does not deviate when the "shell" is rolled 180 degrees in the chamber. On a badly calibrated unit, this would result in the red dot drifting to the other side of the scope. but in this case it remains perfectly still. The carry case is a nice addition as well.Only downside, no off button, you have to remove the batteries. But, just like those lighted Christmas decorations with preloaded batteries, you can just insert a small piece of plastic between the last cell's positive side, and the screw on cap to make your own manual off switch.