The Faithfull Professional Metric Fully Ground HSS Twist Drill Bit Sets are manufactured from high quality M2 grade tool steel, to meet the requirements of the DIN 338 standard. Robust plastic storage cases protect the drills when stored. Suitable for use in: Alloy Steels, Carbon Steels, Cast Iron, Hardened Alloy Steels, Stainless Steels. 10 Piece SET10PRO: 10 Drills: 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10mm.13 Piece SET13PRO: 13 Drills: 1.5, 2, 2.5, 3, 3.2, 3.5, 4, 4.2, 4.5, 5, 5.5, 6 and 6.5mm.