The metabo hss tin drill bit set is suitable for drilling steel and cast steel alloyed and unalloyed grey cast iron non ferrous metals and plastic up to 900 nmm tensile strength the bits are coated with a titanium nitrate alloy with a ground cylindrical type n 135 crosswise grinding tip and gold coloured surface finish they are not suitable for aluminium they are supplied in a metal tin and it contains one of each size 1 15 2 25 3 35 4 45 5 55 6 65 7 75 8 85 9 95 10mm