DRO's have two philosophies, top of the line, absolute accuracy and/or just enough to get you by. Depending on what you want will help determine what you will put on for a DRO. The quality of machine will also dictate the level of precision it is capable of maintaining. No matter what you decide to get, it needs to meet your needs or you will be wasting time to install it. I have a mid grade machine, I am planning on installing a DRO that is better than the mill so I never have to worry that the DRO is ever a problem when I make a mistake. I have machines at work (I fix them) that hold .00005 tolerances, the scales make the quality in any DRO. Even if the machine has a problem, the good DRO's can read the difference in the machine. Some even have temperature compensation. Pick wisely and balance the needs vs. potential. Good luck. Tim