I recently ordered a Mark III tactical ACOG style scope with a small DDAB red dot mounted on top. It would not zero even at 100 yards. I contacted the company and was told to send it in. They were very fast and courteous. I received a new red dot and it will also not zero. They told me that I would have to tilt the scope mount to the side to get it to work. No success. I then mounted the red dot on my PS90 just to see if I was crazy. Nope, the dot would not even zero on a flat rail at 100 yards. Looking through the dot window with a flat elevation (directly behind it) I cannot even see the dot. I have to tilt my head down to the right - the dot is sky high to the left at its lowest and farthest right setting. Lets just say I'm disappointed. I will be contacting them again to request that they actually check to make sure the sight they send me is of passable quality. 3 stars for service. That might change in the future.