Thickness 2.5cm, groove diameter 76mm. Thickness 3.5cm, groove diameter 76mm. The groove moves to the center of the plate, the powder cup can be closer to the powder outlet, the bottom of the magnetic design, the powder plate will not move when the grinder is working. About the magnet under the bottom, I do all N pole on the top, and the machine's magnet has a 50% probability will repel. If it is repulsive, please unscrew the screw in the center of the base of the bean mill, and the magnet can be turned over.