Offers two grading functions in one: it acts as a concentrator to classify grain according to specific weight and as a stone separator. When the material enters the control zone, it is crossed by an air current from top to bottom which allows the material to stratify according to specific weight. The heavier materials then fall through a wider door and are directed to the explo‐tor zone. This mechanism greatly reduces the work of the spinner and improves the overall efficiency of the machining process.