【Professional twist drills】Set of 13 pieces: 1.5 mm (1/16"), 2 mm (5/64"), 2.5 mm (3/32"), 3 mm (7/64"), 3.2 mm (1/8"), 3.5 mm (9/16"). 64" / 162.6 cm cm), 4mm (5/32"), 4.5mm (11/64"), 4.8mm (3/16"), 5mm (13/64"), 5.5mm (7/32"), 6mm (15/64"), 6.5mm (15/64") /10.2 cm High Quality Material: The drill bits are made of high speed steel with a coating of titanium, which is super heat resistance and long service life. Quick Drill Bit Replacement: The 1/4" hex handle is suitable for all power tools, which is easier/more convenient/safe to use. It is suitable for power tools screwdriver, drill, etc. or standard drill chuck. Smooth Drilling: Designed as a 135° cutting angle, which can automatically center and quickly penetrate with a little pressure. Thread grooves can Remove chips and dirt better and quickly.