Bigger than expected, I want paying attention to the size, just didn't want screw holes. It works great.
Mill marks may be slightly deeper than what you want. But can be lapped lower with a flat stone. Since its bigger than your average sharpening stone it may be tougher to keep flat, but not a big concern now. There was a slight bump up at one of the corners, but it can be either avoided or flattened.
