This is an update to a review I left Dec 16. There are two parts to this. First, I heard back from product support from Fret Guru on this, and they were VERY proactive in resolving this issue with me. Something just slipped under the radar on this part and I received a replacement unit in short order. Customer satisfaction is obviously a high priority to them. Second, since my previous review, I've had a chance to to some metrology on this device. I have access to a laser interferometer, and the flatness truly is down into the low tenths as claimed. This beam measured nearly an order of magnitude better than a popular competitors I have, (which I paid twice as much money for). I would definitely recommend this if you want a nice well made flat reference. Given these two points in my updated review, I'm updating my rating to 5-stars