British Gypsum Drywall Screws are phosphate-coated for corrosion resistance, and have self-tapping points to help you reliably and securely fix plasterboard linings. Plasterboard linings must be fixed securely to achieve optimum fire and acoustic performance. These drywall screws let you fix plasterboard lining thicknesses of up to 40mm to metal and 25mm to timber frames.