Our standard grinding is .002″ over 24″, and it may actually be better but, if you have to have ultimate precision,  we recently have found a partner in our area who can deliver the HIGHEST POSSIBLE GRINDING TOLERANCES for our line of modular plates. We call it SUPER GRIND (+/-.0003 over 50″ on parallelism). Check the box when you order. It will take a few extra days, but it will be the best grind that is possible.