Ihave a nikon scope that I have sent back 3 times It pareflex, can not get set .

Parallax error is something that could be different in 2 people. What might be ok to some, will be a nightmare to others. Most scopes are set to parallax at 100 yards, but if you set up your rifle where it wont move, vice, box, pads, peek through the scope to a target at 50 yards, move your head back and forth, up and down, do the crosshairs move with you? How about 25 yards, 100 yards? where it doesn't move is where it is set, and where you find the most accuracy in your scope. It is not hard to hold steady, once you get the hang of it, instead of moving your head to set the crosshairs, anchor your rifle to your cheek and shoulder and move your rifle to the target. There are volumes of material written about this stuff. . Hope this helps.