Drywall screw are designed for drywall to cold-formed steel. these wallboard screws feature a common bugle head that sits flush with the drywall once installed. These plasterboard screws are often used for wood and other materials connect. Raw material are low carbon steel C1022A, After heat treatment sheetrock screws surface hardness up to MIN 550HV, core hardness up to 240-450HV. Plasterboard to plasterboard screws surface include Black Phosphate / Gavanize / Grey phosphate. Ect.