self tapping drywall screw material: steel Drywall screw are widly used with plasterboard. Self tapping screw: Diameter: 3.5mm(#6),3.9mm(#7),4.2mm(#8),4.8mm(#10) Length: 25mm,35mm,50mm....Coating: Black Phosphated,Grey Phosphated,Zinc,Yellow Zinc,Packing: Rugular