The directions to center the thing didn't work. In fact I can't see any difference no matter what I screw or unscrew, tighten or untighten. I am starting to get the feeling I was duped. I will keep trying because if it actually worked then it would be nice to have. I am rooting for the stupid thing but I have had it for weeks now and every time I pick it up it makes me grumble because of the cost and the fact I haven't used it a single time. A $10 wobbler is more accurate than it is.