PVC Airsoft BBs will produce corrosive gas during injection molding. The PH value is acidic and corrosive to mold steel. Therefore, the service life of the mold for making PVC Airsoft BBs with ordinary mold steel will be very short, and the injection molded plastic The surface of the ball is not smooth, and the PVC Airsoft BB mold should be made of special mold steel. Generally, S136 mold steel is used to make the PVC Airsoft BB mold.