Unstable and unusable - HiViz Magnetic Shotgun Sight

The instructions are simple enough to follow ... and then I realized that they're simple because there's nothing to do - the darn thing slips all over the barrel (unless you never fire the weapon, in which case it works great).
Pros: very high visibility
Cons: unstable, doesn't stay in place at all

This review was written in the old system and had content requirements that are different than reviews written today.