Material: High Speed Steels & Type: 6mm, 8mm, 12mm, 16mm, 19mm & Quantity: 1 set (6 Drills) & Length: 48mm / 1.88''. Heat Treatment: Countersink drill bit, high frequency quenching to improve hardness. Unique Design: 5 flute chamfering countersink drill bit for easy removal of debris and cleaning of holes. Versatile Countersink: Countersink is suitable for making 90 degree holes in wood, plastic and soft metals. Suitable for DIY, Home and General Construction / Engineering Use. Please Note: Do not use these countersink drill bits on high hardness metal materials!