Atoma Diamond Plate #400The Atoma Diamond plate #400 grit is the gold standard for whetstone flattening. It removes material extremely quickly and allows you to flatten your stones with relative ease. While other synthetic truing stones will abrade and wear over time they will tend to lose their flatness especially quickly when truing exceptionally wonky stones. The Atoma in comparison is mounted on a solid aluminum block that will remain flat through all the highs and lows