Size: Countersink drill bit set with 3 different sizes: 12mm, 16mm, 19mm, ideal for wood openings, reaming, chamfering, screw head, etc. Standard 1/4'' hex shank drill bit for quick and convenient changing, improving your work efficiency. High Quality: Countersink drill bits are made of high quality carbon steel with high frequency quenching treatment, high hardness and toughness, wear resistance. 5 flutes design with staggered cutting teeth to ensure free chip flow and fast cutting. Wide Usage: Countersink is perfect for wood openings, boring, chamfering, screw heads, etc.; suitable for soft metals, wood, rubber, plastic.