Abstract: A group of trays is configured for storing and transporting workpieces. Each tray includes a base and a frame. The base includes a plurality of receiving portion for receiving the workpieces. The frame surrounds the base to form a cavity. A plurality of projections are formed at the outer side of the flange. When two trays are stacked whether in a same direction or opposite direction, the lower tray is partially received in the cavity of the upper tray, and the projections of the lower tray resist the frame of the upper tray to stop the lower tray from being further inserted into the cavity of the upper tray.