If you are not able to place your eye directly in the center of the optics the target will move off the zero. There really is a very small "sweet spot" directly in the center that maintains the zero. So it is very difficult to use unless you can take the time to position your eye properly. Your groupings will be poor.
Pros: Inexpensive, nice features, easy to mount
Cons: Large sighting paralax problem
This review was written in the old system and had content requirements that are different than reviews written today.